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A–Z Mathematics Codex & Repository

The A–Z Mathematics Index

An alphabetical concordance cataloging mathematical definitions, conceptual intuition ("what it does"), step-by-step procedures ("how to do it"), and worked step-by-step exemplars across all 12 grades.

Grade Level:
Specific Grade:
Domain:
Showing 33 of 33 indexed mathematical concepts
A

A — Concepts

4 terms

Absolute Value & The Integer Domain

/ˈæbsəluːt ˈvæljuː/ • Latin: "absolutus" (freed, unbound by direction)
6th Grade Pre-Algebra
Formal Definition & Rule

The non-negative magnitude of a real number on the continuous number line, representing its geometric distance from origin zero ($0$) irrespective of direction.

$$|x| = \begin{cases} x & \text{if } x \ge 0 \ -x & \text{if } x < 0 \end{cases}$$
What It Does & Why It Matters

It quantifies pure magnitude where direction or sign is irrelevant, such as deviations, financial deficits, depth below sea level, or physical distance.

How to Do It (Step-by-Step)
  • 1 Locate the coordinate $x$ on the real number line.
  • 2 Measure the spatial distance between $x$ and $0$.
  • 3 Drop any negative sign: distance is always non-negative ($|-7| = 7$, $|+7| = 7$).
Worked Exemplum

Problem: Evaluate $|-18| + |12| - |-5|$.

Solution: $|-18| = 18$, $|12| = 12$, and $|-5| = 5$. Compute: $18 + 12 - 5 = 30 - 5 = 25$.

Q.E.D. ∎

Addition Regrouping & Decomposition (Carrying)

/riːˈɡruːpɪŋ/ • Old French: "groupe" (cluster or bundle)
2nd Grade Arithmetic
Formal Definition & Rule

The algorithmic process of composing a single higher base-ten unit whenever the sum of digits in an existing column equals or exceeds the base value ($10$).

$$\text{If } O_1 + O_2 \ge 10 \implies \text{Bundle 10 Ones into 1 Ten}$$
What It Does & Why It Matters

It preserves place value integrity by ensuring no single digit slot ever exceeds $9$, allowing infinite multi-digit addition.

How to Do It (Step-by-Step)
  • 1 Align addends vertically by column (Hundreds, Tens, Ones).
  • 2 Add the Ones column. If the sum is 10 or greater, record the ones digit below and carry the tens bundle above the next column.
  • 3 Add the Tens column, remembering to include any carried bundle.
Worked Exemplum

Problem: Compute $48 + 37$ with vertical regrouping.

Solution: Ones: $8 + 7 = 15$. Record 5 in ones, carry 1 ten. Tens: $1 \text{ (carried)} + 4 + 3 = 8$. Final sum: $85$.

Q.E.D. ∎

Area of Rectangles & Polygons

/ˈeəriə/ • Latin: "area" (open space, vacant threshing floor)
3rd Grade Geometry
Formal Definition & Rule

The total two-dimensional surface enclosed within a closed boundary, quantified as the aggregate count of square unit tiles ($1 \times 1$) that tile the planar region without overlaps.

$$A = l \times w = b \times h$$
What It Does & Why It Matters

It measures planar coverage: flooring, carpeting, painting walls, solar panel arrays, and farming plots.

How to Do It (Step-by-Step)
  • 1 Measure the perpendicular linear length ($l$) and linear width ($w$) in matching units.
  • 2 Multiply length by width: $A = l \times w$.
  • 3 Attach square units to the product ($\text{in}^2, \text{cm}^2, \text{m}^2$).
Worked Exemplum

Problem: A classroom rug measures $8\text{ ft}$ long and $6\text{ ft}$ wide. Calculate the total floor area covered.

Solution: $A = l \times w = 8 \times 6 = 48\text{ sq ft}$.

Q.E.D. ∎

Axiomatic Triangle Congruence (SSS, SAS, ASA, AAS, HL)

/ˈkɒŋɡruəns/ • Latin: "congruere" (to agree together, correspond exactly)
10th Grade / Geom Geometry
Formal Definition & Rule

Geometric postulates establishing that two triangles possess identical size and shape if a specific subset of corresponding sides and angles are proven equal.

$$\Delta ABC \cong \Delta DEF \iff \text{Rigid Motion Maps } \Delta ABC \to \Delta DEF$$
What It Does & Why It Matters

It allows rigorous mathematical proof: once two triangles are proven congruent by 3 pieces of criteria, all 6 corresponding parts are guaranteed congruent (CPCTC).

How to Do It (Step-by-Step)
  • 1 Identify given information and mark congruent side and angle pairs on the diagram.
  • 2 Look for shared sides (Reflexive Property) or vertical angles.
  • 3 Match to a valid congruence criteria (SSS, SAS, ASA, AAS, or Hypotenuse-Leg for right triangles). Never use unproven configurations like SSA or AAA.
Worked Exemplum

Problem: Two triangles share side $AC$. Side $AB \cong AD$ and $\angle BAC \cong \angle DAC$. Prove $\Delta ABC \cong \Delta ADC$.

Solution: $AB \cong AD$ (Side), $\angle BAC \cong \angle DAC$ (Angle), and $AC \cong AC$ (Side via Reflexive Property). Triangles are congruent by $\text{SAS Congruence Postulate}$.

Q.E.D. ∎
B

B — Concepts

2 terms

Base-Ten Place Value (Tens & Ones)

/beɪs tɛn pleɪs ˈvæljuː/ • Latin: "decimalis" (of tenths)
1st Grade Arithmetic
Formal Definition & Rule

The value of a digit determined strictly by its position within a number, where each unit in the tens column equals an aggregate group of ten individual single units.

$$\text{Two-Digit Number} = (T \times 10) + (O \times 1)$$
What It Does & Why It Matters

It allows humans to express any quantity using only ten symbols ($0$ through $9$) by bundling groups into bundles of ten, avoiding the need for infinite distinct numeral marks.

How to Do It (Step-by-Step)
  • 1 Count out the total single units into complete bundles of ten.
  • 2 Write the count of complete 10-bundles in the left column (Tens).
  • 3 Write any remaining loose single units in the right column (Ones).
Worked Exemplum

Problem: Decompose the quantity $47$ into its foundational base-ten components.

Solution: 47 contains 4 bundles of ten and 7 loose units: $47 = (4 \times 10) + (7 \times 1) = 40 + 7$.

Q.E.D. ∎

Binomial Theorem & Pascal Combinatorics

/baɪˈnoʊmiəl/ • Latin: "bi" (two) + "nomen" (name/term)
11th Grade / Alg II Algebra II
Formal Definition & Rule

An algebraic formula providing the expanded polynomial terms of any binomial power $(a+b)^n$, using combinatoric binomial coefficients from Pascal's Triangle.

$$(a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k \quad \left(\binom{n}{k} = \frac{n!}{k!(n-k)!}\right)$$
What It Does & Why It Matters

It bypasses manual, error-prone repeated polynomial multiplications (like multiplying $(a+b)$ five times), expanding higher-degree powers in a single structured sweep.

How to Do It (Step-by-Step)
  • 1 Identify row $n$ in Pascal's Triangle to obtain coefficients $\binom{n}{k}$.
  • 2 Write descending powers of $a$ from $a^n$ down to $a^0$.
  • 3 Write ascending powers of $b$ from $b^0$ up to $b^n$.
  • 4 Multiply coefficients and variable powers together for each term.
Worked Exemplum

Problem: Expand $(x + 2)^3$ using the Binomial Theorem.

Solution: Row 3 coefficients: $1, 3, 3, 1$. Expand: $1(x^3)(2^0) + 3(x^2)(2^1) + 3(x^1)(2^2) + 1(x^0)(2^3) = x^3 + 6x^2 + 12x + 8$.

Q.E.D. ∎
C

C — Concepts

4 terms

Circle Geometry: Circumference & Area

/səˈkʌmfərəns/ • Greek: "π" (perimetros, circumference)
7th Grade Geometry
Formal Definition & Rule

Geometric relationships for any Euclidean circle, where Circumference ($C$) is the boundary perimeter and Area ($A$) is the internal planar surface, both governed by the transcendental constant $\pi \approx 3.14159$.

$$C = 2\pi r = \pi d, \quad A = \pi r^2$$
What It Does & Why It Matters

It allows precise calculation of round perimeters (wheels, tracks) and circular surface areas (pipes, pizza slices, fields) from a single radial measurement.

How to Do It (Step-by-Step)
  • 1 Identify radius ($r$). If given diameter ($d$), divide by $2$ ($r = d/2$).
  • 2 For perimeter/circumference, compute $C = 2 \times \pi \times r$.
  • 3 For interior surface area, square the radius first ($r^2$), then multiply by $\pi$: $A = \pi \times r^2$.
Worked Exemplum

Problem: A circular trampoline has a radius of $7\text{ ft}$. Calculate its exact circumference and area in terms of $\pi$.

Solution: Circumference: $C = 2\pi(7) = 14\pi\text{ ft}$. Area: $A = \pi(7^2) = 49\pi\text{ sq ft}$.

Q.E.D. ∎

Commutative Property of Addition

/kəˈmjuːtətɪv/ • Latin: "commutare" (to interchange or swap)
1st Grade Arithmetic
Formal Definition & Rule

An algebraic axiom stating that changing the physical or conceptual order of addends does not alter their collective sum.

$$a + b = b + a$$
What It Does & Why It Matters

It halves the memory required for mental math fact fluency: if you know $3 + 8 = 11$, you automatically know $8 + 3 = 11$.

How to Do It (Step-by-Step)
  • 1 Identify the two addends being combined.
  • 2 Start with the larger number first to minimize manual counting efforts (Count-On Strategy).
  • 3 Add the smaller addend: the resulting sum is invariant.
Worked Exemplum

Problem: Calculate $2 + 9$ using the Commutative Property.

Solution: Swap addends: $2 + 9 = 9 + 2$. Count on 2 units from 9: $9 \to 10 \to 11$. Sum is $11$.

Q.E.D. ∎

Complex Numbers & The Imaginary Unit

/ˈkɒm.plɛks/ • Latin: "complexus" (interwoven, composite of real and imaginary)
11th Grade / Alg II Algebra II
Formal Definition & Rule

An extension of the one-dimensional real number system into a two-dimensional complex plane ($\mathbb{C}$), defined by the imaginary unit $i$ whose square equals $-1$.

$$z = a + bi \quad (i = \sqrt{-1}, \; i^2 = -1, \; a, b \in \mathbb{R})$$
What It Does & Why It Matters

It eliminates the barrier of negative square roots, guaranteeing that every $n$-th degree polynomial has exactly $n$ complex roots (Fundamental Theorem of Algebra). Powers electrical engineering and quantum physics.

How to Do It (Step-by-Step)
  • 1 Treat $i$ algebraically like a variable, combining real parts with real parts and imaginary parts with imaginary parts: $(a + bi) + (c + di) = (a+c) + (b+d)i$.
  • 2 When multiplying, expand via FOIL and replace any occurrence of $i^2$ with $-1$.
  • 3 To divide, multiply numerator and denominator by the complex conjugate $a - bi$.
Worked Exemplum

Problem: Multiply $(3 + 2i)(1 - 4i)$.

Solution: FOIL: $3(1) + 3(-4i) + 2i(1) + 2i(-4i) = 3 - 12i + 2i - 8i^2$. Replace $i^2 = -1$: $3 - 10i - 8(-1) = 3 - 10i + 8 = 11 - 10i$.

Q.E.D. ∎

Constant of Proportionality (Unit Rate)

/prəˌpɔːʃəˈnæləti/ • Latin: "pro portione" (according to the share)
7th Grade Proportions
Formal Definition & Rule

The invariant multiplicative ratio ($k$) between two directly proportional quantities $x$ and $y$, representing the steepness of a linear relationship passing through the origin $(0, 0)$.

$$y = kx \implies k = \frac{y}{x}$$
What It Does & Why It Matters

It describes uniform rate behaviors: speed ($d = rt$), wage rates ($\text{Pay} = r \times \text{Hours}$), scaling recipes, and currency conversion.

How to Do It (Step-by-Step)
  • 1 Pick any non-zero ordered coordinate pair $(x, y)$ from a proportional table or graph.
  • 2 Divide the dependent variable $y$ by independent variable $x$: $k = \frac{y}{x}$.
  • 3 Verify that all other pairs $(x_i, y_i)$ yield the identical quotient $k$.
Worked Exemplum

Problem: A car travels $165\text{ miles}$ in $3\text{ hours}$ at constant speed. Find the constant of proportionality and the equation relating distance ($y$) and hours ($x$).

Solution: $k = \frac{y}{x} = \frac{165}{3} = 55\text{ mph}$. Direct proportional equation: $y = 55x$.

Q.E.D. ∎
D

D — Concepts

2 terms

Derivative via Difference Quotient

/dɪˈrɪvətɪv/ • Latin: "derivare" (to draw off from a source stream)
12th Grade / Calc Calculus
Formal Definition & Rule

The instantaneous rate of change of a differentiable continuous function with respect to its independent variable, geometrically representing the exact slope of the tangent line at any point $x$.

$$f'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x)}{h}$$
What It Does & Why It Matters

It freezes continuous motion at a single infinitesimal point in time, revealing exact velocities, rates of biological growth, and market volatility.

How to Do It (Step-by-Step)
  • 1 Substitute $x + h$ into the function $f(x)$ to evaluate $f(x + h)$.
  • 2 Formulate the difference quotient: $\frac{f(x + h) - f(x)}{h}$.
  • 3 Algebraically cancel the factor of $h$ from the denominator.
  • 4 Evaluate the limit by taking $h \to 0$.
Worked Exemplum

Problem: Find the derivative of $f(x) = x^2$ using the limit definition.

Solution: $\lim_{h \to 0} \frac{(x+h)^2 - x^2}{h} = \lim_{h \to 0} \frac{x^2 + 2xh + h^2 - x^2}{h} = \lim_{h \to 0} \frac{2xh + h^2}{h} = \lim_{h \to 0} (2x + h) = 2x$.

Q.E.D. ∎

Distributive Property of Multiplication

/dɪˈstrɪbjʊtɪv/ • Latin: "distribuere" (to apportion or divide up)
3rd Grade Algebra & Ops
Formal Definition & Rule

An algebraic theorem stating that multiplying a multiplier by a partitioned sum yields identical results to multiplying each part individually and summing the partial products.

$$a \times (b + c) = (a \times b) + (a \times c)$$
What It Does & Why It Matters

It allows complex mental arithmetic by breaking intimidating numbers (like $7 \times 14$) into two effortless friendly facts ($7 \times 10 + 7 \times 4$).

How to Do It (Step-by-Step)
  • 1 Break one tough factor into two easier additive parts (e.g., $14 = 10 + 4$).
  • 2 Multiply the outside multiplier by the first decomposed part.
  • 3 Multiply the outside multiplier by the second decomposed part.
  • 4 Add the two partial products together.
Worked Exemplum

Problem: Evaluate $8 \times 13$ using the Distributive Property.

Solution: Decompose $13 = 10 + 3$: $8 \times (10 + 3) = (8 \times 10) + (8 \times 3) = 80 + 24 = 104$.

Q.E.D. ∎
E

E — Concepts

2 terms

Euclidean Division Algorithm (Long Division)

/lɔːŋ dɪˈvɪʒən/ • Latin: "divisio" (distribution among shares)
4th Grade Arithmetic
Formal Definition & Rule

An iterative place-value algorithm that determines how many times a positive integer divisor ($b$) partitions into a dividend ($a$), yielding an integer quotient ($q$) and an exact remainder ($r$).

$$a = bq + r \quad (0 \le r < b)$$
What It Does & Why It Matters

It enables the exact and step-by-step division of arbitrarily large multi-digit numbers by breaking the computation down column-by-column.

How to Do It (Step-by-Step)
  • 1 Divide: Determine how many times the divisor fits into the current active place-value digit(s).
  • 2 Multiply: Multiply the resulting quotient digit by the divisor.
  • 3 Subtract: Subtract that product from the active digits to find the local remainder.
  • 4 Bring Down: Bring down the next digit of the dividend and repeat.
Worked Exemplum

Problem: Divide $496 \div 4$ using the standard long division algorithm.

Solution: $4 \div 4 = 1$ (rem 0). Bring down 9: $9 \div 4 = 2$ ($2 \times 4 = 8$, rem 1). Bring down 6: $16 \div 4 = 4$ ($4 \times 4 = 16$, rem 0). Quotient is $124$.

Q.E.D. ∎

Exponential Growth & Decay Models

/ˌɛkspəˈnɛnʃəl/ • Latin: "exponere" (to exhibit, put forth into powers)
9th Grade / Alg I Algebra I
Formal Definition & Rule

A non-linear mathematical model where the rate of change is proportional to the current amount, resulting in geometric compounding over continuous or discrete time intervals $t$.

$$y = a(1 \pm r)^t \quad \left(\text{Growth: } +r, \; \text{Decay: } -r\right)$$
What It Does & Why It Matters

It accurately models viral contagion, compound investment interest, population explosions, and radioactive carbon decay.

How to Do It (Step-by-Step)
  • 1 Identify initial amount ($a$) and decimal rate of change ($r$).
  • 2 Construct the growth factor ($1 + r$) or decay factor ($1 - r$).
  • 3 Substitute elapsed time periods ($t$) into the exponent and evaluate.
Worked Exemplum

Problem: A colony of $500$ bacteria doubles ($r = 1.0$) every hour. How many bacteria exist after $4\text{ hours}$?

Solution: $y = a(1 + r)^t = 500(1 + 1)^4 = 500(2^4) = 500(16) = 8,000\text{ bacteria}$.

Q.E.D. ∎
F

F — Concepts

4 terms

Factoring Quadratic Trinomials

/ˈfæk.tər.ɪŋ/ • Latin: "factor" (a maker, doer, or constituent part)
9th Grade / Alg I Algebra I
Formal Definition & Rule

The algebraic decomposition of a quadratic trinomial into the product of two linear binomial factors, reversing the FOIL distributive expansion.

$$x^2 + (p + q)x + pq = (x + p)(x + q)$$
What It Does & Why It Matters

By applying the Zero Product Property ($AB = 0 \implies A=0 \text{ or } B=0$), factoring converts complex polynomial expressions into simple solvable linear equations.

How to Do It (Step-by-Step)
  • 1 Look for two integers $p$ and $q$ that multiply to constant $c$ ($p \times q = c$) and add to middle coefficient $b$ ($p + q = b$).
  • 2 Construct the binomials: $(x + p)(x + q)$.
  • 3 Check work by expanding via FOIL (First, Outside, Inside, Last).
Worked Exemplum

Problem: Factor the polynomial $x^2 + 7x + 12$.

Solution: Find two numbers that multiply to $12$ and add to $7$: $3 \times 4 = 12$ and $3 + 4 = 7$. Factored form: $(x + 3)(x + 4)$.

Q.E.D. ∎

Fraction Addition with Unlike Denominators

/ʌnˈlaɪk dɪˈnɒmɪneɪtərz/ • Latin: "denominare" (to name or specify)
5th Grade Fractions
Formal Definition & Rule

The method of renaming fractions into equivalent representations sharing a common unit measure (the Least Common Denominator) prior to combining numerators.

$$\frac{a}{b} + \frac{c}{d} = \frac{ad + bc}{bd}$$
What It Does & Why It Matters

Fractions cannot be added directly if their pieces are different sizes (e.g. halves and thirds); finding the LCD cuts all pieces into identical units so they can be summed.

How to Do It (Step-by-Step)
  • 1 Find the Least Common Multiple (LCM) of denominators $b$ and $d$.
  • 2 Multiply numerator and denominator of each fraction by the factor needed to attain the LCD.
  • 3 Add the newly aligned numerators while keeping the common denominator constant.
  • 4 Simplify to lowest terms if possible.
Worked Exemplum

Problem: Compute $\frac{2}{3} + \frac{1}{4}$.

Solution: $\text{LCM}(3, 4) = 12$. Scale fractions: $\frac{2 \times 4}{3 \times 4} = \frac{8}{12}$, $\frac{1 \times 3}{4 \times 3} = \frac{3}{12}$. Add: $\frac{8 + 3}{12} = \frac{11}{12}$.

Q.E.D. ∎

Fraction Division via Reciprocal (Keep-Change-Flip)

/rɪˈsɪprəkəl/ • Latin: "reciprocus" (moving back and forth, alternating)
6th Grade Fractions
Formal Definition & Rule

An algebraic law establishing that dividing by a rational fraction is mathematically equivalent to multiplying by its multiplicative inverse (reciprocal).

$$\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c} = \frac{ad}{bc}$$
What It Does & Why It Matters

Division answers "how many groups fit inside." Multiplying by the flipped reciprocal counts how many sub-units fit without laborious manual partitioning.

How to Do It (Step-by-Step)
  • 1 Keep: Leave the dividend (first fraction) unchanged.
  • 2 Change: Invert the division operator ($\div$) into multiplication ($\times$).
  • 3 Flip: Invert the divisor (second fraction) into its reciprocal ($\frac{c}{d} \to \frac{d}{c}$).
  • 4 Multiply straight across and reduce.
Worked Exemplum

Problem: Compute $\frac{3}{4} \div \frac{2}{5}$.

Solution: Keep $\frac{3}{4}$, Change $\div$ to $\times$, Flip $\frac{2}{5} \to \frac{5}{2}$: $\frac{3}{4} \times \frac{5}{2} = \frac{3 \times 5}{4 \times 2} = \frac{15}{8} = 1\frac{7}{8}$.

Q.E.D. ∎

Fundamental Theorem of Calculus (FTC)

/ˌfʌndəˈmɛntl ˈθɪərəm/ • Latin: "fundamentum" (groundwork, base cornerstone)
12th Grade / Calc Calculus
Formal Definition & Rule

The unifying theorem of mathematical analysis demonstrating that differentiation and integration are inverse operations: the definite integral (net accumulated area) can be calculated via anti-derivatives.

$$\int_{a}^{b} f(x) \, dx = F(b) - F(a) \quad \left(\text{where } F'(x) = f(x)\right)$$
What It Does & Why It Matters

It bridges geometry (accumulating area under curves) with algebra (reversing derivatives), enabling exact calculation of areas, volumes of revolution, and total physical work.

How to Do It (Step-by-Step)
  • 1 Find the antiderivative function $F(x)$ such that $F'(x) = f(x)$.
  • 2 Evaluate the antiderivative at the upper integration limit ($F(b)$).
  • 3 Evaluate the antiderivative at the lower integration limit ($F(a)$).
  • 4 Subtract: $\text{Net Area} = F(b) - F(a)$.
Worked Exemplum

Problem: Evaluate the definite integral $\int_{0}^{3} 2x \, dx$.

Solution: Antiderivative of $2x$ is $F(x) = x^2$. Evaluate: $F(3) - F(0) = 3^2 - 0^2 = 9 - 0 = 9$.

Q.E.D. ∎
G

G — Concepts

1 term

Greatest Common Factor (GCF) & Euclidean Algorithm

/ˈɡreɪtɪst ˈkɒmən ˈfæktər/ • Greek: "arithmos" (prime numbers)
6th Grade Number Theory
Formal Definition & Rule

The largest natural number that evenly divides two or more integers without leaving a remainder, forming the basis of simplifying fractions.

$$\gcd(a, b) = \gcd(b, a \bmod b) \quad (\gcd(a, 0) = a)$$
What It Does & Why It Matters

It finds the maximum bundle size when grouping disparate collections into identical subsets, and reduces fractions to their simplest indivisible terms.

How to Do It (Step-by-Step)
  • 1 Find the prime factorizations of both numbers.
  • 2 Identify all common prime factors shared by both sets.
  • 3 Multiply the shared common prime factors together to obtain the GCF.
Worked Exemplum

Problem: Find the Greatest Common Factor of $24$ and $36$.

Solution: Prime factorization: $24 = 2^3 \times 3$, $36 = 2^2 \times 3^2$. Common prime factors: $2^2 \times 3 = 4 \times 3 = 12$. $\text{GCF} = 12$.

Q.E.D. ∎
I

I — Concepts

1 term

Indefinite Integrals & Antidifferentiation

/ˈɪndɛfɪnɪt ˈɪntɪɡrəl/ • Latin: "integrare" (to make whole, aggregate)
12th Grade / Calc Calculus
Formal Definition & Rule

The complete family of antiderivative functions whose instantaneous derivative equals the integrand $f(x)$, unified by the arbitrary constant of integration $C$.

$$\int x^n \, dx = \frac{x^{n+1}}{n+1} + C \quad (n \ne -1)$$
What It Does & Why It Matters

It reconstructs total distance from velocity data, or total accumulated charge from electric current, reversing the derivative process.

How to Do It (Step-by-Step)
  • 1 Identify each power term $x^n$.
  • 2 Add $1$ to the exponent ($n \to n + 1$).
  • 3 Divide by the new exponent ($n + 1$).
  • 4 Append the arbitrary integration constant $+ C$.
Worked Exemplum

Problem: Find the indefinite integral $\int (3x^2 + 4x - 5) \, dx$.

Solution: $\int 3x^2 dx = x^3$; $\int 4x dx = 2x^2$; $\int -5 dx = -5x$. Combine: $x^3 + 2x^2 - 5x + C$.

Q.E.D. ∎
L

L — Concepts

2 terms

Linear Slope-Intercept Form

/sloʊp ˈɪntərsɛpt/ • Latin: "intercipere" (to catch or cross between)
8th Grade Linear Algebra
Formal Definition & Rule

The canonical algebraic representation of a two-dimensional straight line, where $m$ signifies the constant rate of change (slope) and $b$ represents the coordinate value where the line intercepts the vertical y-axis ($(0, b)$).

$$y = mx + b \quad \left(m = \frac{\Delta y}{\Delta x} = \frac{y_2 - y_1}{x_2 - x_1}\right)$$
What It Does & Why It Matters

It enables instant graphing and prediction of linear behaviors, allowing you to project future outcomes with a known starting point ($b$) and velocity ($m$).

How to Do It (Step-by-Step)
  • 1 Calculate the slope $m$ by finding vertical change over horizontal change: $m = \frac{y_2 - y_1}{x_2 - x_1}$.
  • 2 Plot the starting y-intercept $(0, b)$ directly on the vertical axis.
  • 3 Use slope $m = \frac{\text{rise}}{\text{run}}$ to navigate from the intercept to subsequent points, and connect with a line.
Worked Exemplum

Problem: Find the slope-intercept equation of the line passing through $(2, 5)$ and $(4, 11)$.

Solution: Slope: $m = \frac{11 - 5}{4 - 2} = \frac{6}{2} = 3$. Find $b$: $5 = 3(2) + b \implies 5 = 6 + b \implies b = -1$. Equation: $y = 3x - 1$.

Q.E.D. ∎

Logarithms & Power Laws

/ˈlɒɡərɪðəm/ • Greek: "logos" (ratio) + "arithmos" (number)
11th Grade / Alg II Algebra II
Formal Definition & Rule

The inverse mathematical function of exponentiation, answering the question: "To what exponent must the base $b$ be raised to produce the value $x$?"

$$\log_b(x) = y \iff b^y = x \quad (\log(xy) = \log x + \log y)$$
What It Does & Why It Matters

It compresses astronomical multiplicative scales into manageable linear steps (Richter scale earthquakes, pH acidity, decibels of sound, compound interest).

How to Do It (Step-by-Step)
  • 1 Product Rule: Sum of logs equals log of product: $\log(A) + \log(B) = \log(AB)$.
  • 2 Quotient Rule: Difference of logs equals log of quotient: $\log(A) - \log(B) = \log(A/B)$.
  • 3 Power Rule: Pull exponents out front as multipliers: $\log(A^k) = k \log(A)$.
Worked Exemplum

Problem: Condense into a single logarithm: $2\log_3(x) + \log_3(5)$.

Solution: Apply Power Rule: $\log_3(x^2) + \log_3(5)$. Apply Product Rule: $\log_3(5x^2)$.

Q.E.D. ∎
M

M — Concepts

1 term

Measures of Center: Mean, Median & Mode

/miːn ˈmiːdiən moʊd/ • Latin: "medianus" (of the middle)
6th Grade Statistics
Formal Definition & Rule

Statistical metrics summarizing an entire data distribution into a single representative central value: the arithmetic average (Mean), the 50th percentile midpoint (Median), and the most frequent value (Mode).

$$\bar{x} = \frac{\sum_{i=1}^n x_i}{n}, \quad \text{Range} = \text{Max} - \text{Min}$$
What It Does & Why It Matters

It distills large, noisy empirical datasets into actionable benchmark summaries for test scores, scientific experiments, climate averages, and economic indicators.

How to Do It (Step-by-Step)
  • 1 Mean: Sum all values together, then divide by the total count $n$.
  • 2 Median: Arrange data in ascending numerical order and pick the exact middle value (or average the two middle values if $n$ is even).
  • 3 Mode: Identify the number that appears with highest frequency.
Worked Exemplum

Problem: Calculate the mean and median for the test score dataset: $\{80, 85, 90, 90, 100\}$.

Solution: Mean: $\frac{80+85+90+90+100}{5} = \frac{445}{5} = 89$. Median: Ordered middle value is $90$. Mode is $90$.

Q.E.D. ∎
O

O — Concepts

1 term

Order of Operations (PEMDAS / GEMS)

/ˈɔːrdər əv ˌɒpəˈreɪʃənz/ • Acronym: Parentheses, Exponents, Multiply/Divide, Add/Subtract
6th Grade Pre-Algebra
Formal Definition & Rule

The universal algebraic precedence convention dictating the precise sequence in which arithmetic operations must be evaluated to ensure unambiguous solutions.

$$\text{Hierarchy: } \text{Groupings} \succ \text{Exponents} \succ \{\times, \div\} \succ \{+, -\}$$
What It Does & Why It Matters

It eliminates mathematical chaos: without strict order of operations, an expression like $2 + 3 \times 4$ could be interpreted as either $20$ or $14$.

How to Do It (Step-by-Step)
  • 1 Evaluate inside innermost Parentheses/Groupings first.
  • 2 Evaluate all Exponents and radical roots next.
  • 3 Compute all Multiplications and Divisions from Left to Right.
  • 4 Compute all Additions and Subtractions from Left to Right.
Worked Exemplum

Problem: Evaluate $6 + 4 \times (5 - 2)^2 \div 3$.

Solution: Groupings: $(5-2) = 3$. Exponents: $3^2 = 9$. Multiply/Divide Left-to-Right: $4 \times 9 = 36$, then $36 \div 3 = 12$. Addition: $6 + 12 = 18$.

Q.E.D. ∎
P

P — Concepts

3 terms

Power Rule of Differentiation

/ˈpaʊər ruːl/ • Latin: "potentia" (power, exponent degree)
12th Grade / Calc Calculus
Formal Definition & Rule

An operational shortcut derived from the binomial theorem and difference quotient that computes the instantaneous rate of change of any monomial power function in a single algebraic step.

$$\frac{d}{dx}\left[x^n\right] = n x^{n - 1} \quad (n \in \mathbb{R})$$
What It Does & Why It Matters

It bypasses lengthy limit difference quotient algebra, reducing derivative computation on polynomials to elementary mental arithmetic.

How to Do It (Step-by-Step)
  • 1 Bring the existing exponent $n$ down in front to multiply the term.
  • 2 Subtract exactly $1$ from the power exponent ($n \to n - 1$).
  • 3 If the term has a leading constant $c$, multiply: $\frac{d}{dx}[c x^n] = c \cdot n x^{n-1}$.
Worked Exemplum

Problem: Differentiate $f(x) = 4x^3 - 5x^2 + 7x - 9$.

Solution: $f'(x) = 4(3)x^{3-1} - 5(2)x^{2-1} + 7(1)x^{1-1} - 0 = 12x^2 - 10x + 7$.

Q.E.D. ∎

Prime vs. Composite Numbers

/praɪm/ • Latin: "primus" (first, primordial, indivisible)
4th Grade Number Theory
Formal Definition & Rule

A natural number greater than $1$ is Prime if its only positive divisors are $1$ and itself. A number with more than two distinct positive factors is Composite.

$$\text{Prime: } \{n \in \mathbb{Z}^+ \mid \text{Factors}(n) = \{1, n\}\}$$
What It Does & Why It Matters

Primes act as the multiplicative "atoms" of all mathematics: by the Fundamental Theorem of Arithmetic, every integer has a unique prime factorization.

How to Do It (Step-by-Step)
  • 1 Check if $n \le 1$: $0$ and $1$ are neither prime nor composite.
  • 2 Test trial division by primes up to $\sqrt{n}$ ($2, 3, 5, 7 \dots$).
  • 3 If any divisor divides $n$ without remainder, $n$ is Composite; otherwise, it is Prime.
Worked Exemplum

Problem: Determine whether $29$ and $35$ are prime or composite.

Solution: Factors of $29$: $\{1, 29\} \implies$ Prime. Factors of $35$: $\{1, 5, 7, 35\} \implies$ Composite ($5 \times 7 = 35$).

Q.E.D. ∎

Pythagorean Theorem

/pɪˌθæɡəˈriːən/ • Named after Pythagoras of Samos (c. 570–495 BC)
8th Grade Geometry
Formal Definition & Rule

A fundamental theorem of Euclidean geometry stating that in any right triangle, the area of the square erected upon the hypotenuse ($c$) equals the combined sum of the areas of the squares erected upon legs $a$ and $b$.

$$a^2 + b^2 = c^2 \iff c = \sqrt{a^2 + b^2}$$
What It Does & Why It Matters

It unlocks straight-line distance calculations across two dimensions, forming the basis of navigation, construction, computer graphics, and coordinate geometry.

How to Do It (Step-by-Step)
  • 1 Verify the triangle contains an exact $90^\circ$ right angle.
  • 2 Identify the hypotenuse ($c$), which is strictly opposite the right angle.
  • 3 Square the two known sides. To solve for hypotenuse: $c = \sqrt{a^2 + b^2}$. To solve for a leg: $a = \sqrt{c^2 - b^2}$.
Worked Exemplum

Problem: A right triangle has legs of length $6\text{ cm}$ and $8\text{ cm}$. Find the length of hypotenuse $c$.

Solution: $a^2 + b^2 = c^2 \implies 6^2 + 8^2 = c^2 \implies 36 + 64 = 100 \implies c = \sqrt{100} = 10\text{ cm}$.

Q.E.D. ∎
Q

Q — Concepts

1 term

Quadratic Formula & The Discriminant

/kwɒˈdrætɪk/ • Latin: "quadratus" (squared, four-sided square)
9th Grade / Alg I Algebra I
Formal Definition & Rule

The universal algebraic closed-form solution to any second-degree polynomial equation $ax^2 + bx + c = 0$, where the discriminant ($\Delta = b^2 - 4ac$) determines the nature of the roots.

$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \quad (\Delta = b^2 - 4ac)$$
What It Does & Why It Matters

It solves any parabolic or quadratic equation, even when factoring fails. It models trajectories, projectiles, revenue optimization, and physics mechanics.

How to Do It (Step-by-Step)
  • 1 Set equation into standard form: $ax^2 + bx + c = 0$.
  • 2 Identify coefficients $a, b, c$ with their respective signs.
  • 3 Evaluate the discriminant: $\Delta = b^2 - 4ac$ ($\Delta > 0 \implies 2\text{ real roots}$; $\Delta = 0 \implies 1\text{ root}$; $\Delta < 0 \implies \text{complex roots}$).
  • 4 Compute the two roots via $\pm$ in the numerator.
Worked Exemplum

Problem: Solve $x^2 - 5x + 6 = 0$ using the Quadratic Formula.

Solution: $a=1, b=-5, c=6$. $\Delta = (-5)^2 - 4(1)(6) = 25 - 24 = 1$. $x = \frac{-(-5) \pm \sqrt{1}}{2(1)} = \frac{5 \pm 1}{2} \implies x = 3 \text{ or } x = 2$.

Q.E.D. ∎
R

R — Concepts

2 terms

Rectangular Arrays & Repeated Addition

/əˈreɪ/ • Anglo-Norman: "arrai" (orderly systematic arrangement)
2nd Grade Arithmetic
Formal Definition & Rule

A geometric configuration of discrete objects aligned into identical horizontal rows and vertical columns, serving as the concrete foundation of multiplication.

$$\text{Total Items} = \sum_{i=1}^{r} c = r \times c$$
What It Does & Why It Matters

It bridges counting single items to spatial two-dimensional grouping, proving that multiplication is rapid repeated addition.

How to Do It (Step-by-Step)
  • 1 Count the number of horizontal lines (Rows, $r$).
  • 2 Count how many objects are situated in each single row (Columns, $c$).
  • 3 Add the row count $r$ times, or skip-count by $c$.
Worked Exemplum

Problem: Find the total items in an array containing $4$ rows with $5$ stars in each row.

Solution: Repeated addition of rows: $5 + 5 + 5 + 5 = 20$. The array contains exactly $20$ stars.

Q.E.D. ∎

Right Triangle Trigonometry (SOH-CAH-TOA)

/ˌtrɪɡəˈnɒmətri/ • Greek: "trigonon" (triangle) + "metron" (measure)
10th Grade / Geom Trigonometry
Formal Definition & Rule

Fundamental trigonometric ratios relating the acute reference angle ($\theta$) of a right triangle to dimensionless quotients of its side lengths.

$$\sin\theta = \frac{\text{Opp}}{\text{Hyp}}, \quad \cos\theta = \frac{\text{Adj}}{\text{Hyp}}, \quad \tan\theta = \frac{\text{Opp}}{\text{Adj}}$$
What It Does & Why It Matters

It enables the measurement of inaccessible heights and distances (surveying mountains, celestial navigation, architectural load angles) from a single angle and distance.

How to Do It (Step-by-Step)
  • 1 Anchor your perspective at the acute reference angle $\theta$.
  • 2 Label the three sides: Hypotenuse (longest side opposite $90^\circ$), Opposite (across from $\theta$), and Adjacent (next to $\theta$).
  • 3 Select the matching ratio from SOH-CAH-TOA based on your known and unknown sides, then solve.
Worked Exemplum

Problem: In a right triangle, angle $\theta$ has an opposite side of $5\text{ cm}$ and hypotenuse of $13\text{ cm}$. Find $\sin\theta$ and $\tan\theta$.

Solution: $\sin\theta = \frac{\text{Opp}}{\text{Hyp}} = \frac{5}{13}$. Adjacent side: $\sqrt{13^2 - 5^2} = \sqrt{144} = 12$. Therefore, $\tan\theta = \frac{\text{Opp}}{\text{Adj}} = \frac{5}{12}$.

Q.E.D. ∎
S

S — Concepts

1 term

Systems of Linear Equations (Simultaneous Elimination)

/ˈsɪstəmz/ • Greek: "systema" (organized whole composition)
8th Grade Algebra
Formal Definition & Rule

A set of two or more algebraic equations containing identical variables, whose simultaneous solution is the unique coordinate point where all graphs intersect.

$$\begin{cases} a_1 x + b_1 y = c_1 \ a_2 x + b_2 y = c_2 \end{cases} \implies \text{Intersection Point } (x, y)$$
What It Does & Why It Matters

It models break-even points in economics, mixing chemical solutions, flight intersection paths, and dual-variable constraints.

How to Do It (Step-by-Step)
  • 1 Multiply one or both equations by a constant so that coefficients of one variable are exact opposites.
  • 2 Add the two equations vertically to eliminate that variable.
  • 3 Solve the resulting single-variable equation.
  • 4 Back-substitute into either original equation to find the other variable.
Worked Exemplum

Problem: Solve the linear system: $2x + y = 7$ and $x - y = 2$.

Solution: Add equations: $(2x + y) + (x - y) = 7 + 2 \implies 3x = 9 \implies x = 3$. Substitute: $3 - y = 2 \implies y = 1$. Solution: $(3, 1)$.

Q.E.D. ∎
U

U — Concepts

1 term

Unit Fractions & Rational Partitioning

/ˈjuːnɪt ˈfrækʃən/ • Latin: "fractio" (a breaking into fragments)
3rd Grade Fractions
Formal Definition & Rule

A rational quantity formed by partitioning a single whole into $b$ congruent, equal-sized pieces, where the fraction represents exactly one of those partitioned segments.

$$\text{Unit Fraction} = \frac{1}{b} \quad (b \in \mathbb{Z}^+)$$
What It Does & Why It Matters

It establishes the fundamental atomic building block of all rational numbers: any non-unit fraction $\frac{a}{b}$ is simply $a$ copies of the unit fraction $\frac{1}{b}$.

How to Do It (Step-by-Step)
  • 1 Verify the whole unit is divided into segments of strictly equal size/length.
  • 2 Count the total number of segments to determine the denominator ($b$).
  • 3 Isolate or shade exactly 1 segment to represent $\frac{1}{b}$.
Worked Exemplum

Problem: Express the fraction $\frac{5}{8}$ as an iteration of its underlying unit fraction.

Solution: The unit fraction is $\frac{1}{8}$. Thus: $\frac{5}{8} = \frac{1}{8} + \frac{1}{8} + \frac{1}{8} + \frac{1}{8} + \frac{1}{8} = 5 \times \frac{1}{8}$.

Q.E.D. ∎
V

V — Concepts

1 term

Volume of Rectangular Prisms

/ˈvɒljuːm/ • Latin: "volumen" (roll, scroll, 3D cubic capacity)
5th Grade Geometry
Formal Definition & Rule

The total measure of three-dimensional space enclosed within a solid boundary, quantified as the aggregate number of unit cubes ($1 \times 1 \times 1$) that pack the interior without gaps.

$$V = l \times w \times h = B \times h$$
What It Does & Why It Matters

It measures the physical capacity of solid 3D structures (such as storage containers, shipping boxes, or liquid tanks).

How to Do It (Step-by-Step)
  • 1 Measure the length ($l$) and width ($w$) of the rectangular base to find base area ($B = l \times w$).
  • 2 Measure the perpendicular vertical height ($h$) of the prism.
  • 3 Multiply base area by height: $V = B \times h$. Units are always cubic ($\text{cm}^3, \text{in}^3, \text{m}^3$).
Worked Exemplum

Problem: Find the volume of a rectangular prism with length $6\text{ cm}$, width $4\text{ cm}$, and height $5\text{ cm}$.

Solution: $V = l \times w \times h = 6 \times 4 \times 5 = 24 \times 5 = 120\text{ cm}^3$.

Q.E.D. ∎

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