STEM · Subjects
Formula references and worked examples for the algebra, geometry, trigonometry, and calculus topics that show up most often in coursework and exams.
Foundations
| Concept | Formula |
|---|---|
| Quadratic formula | x = (-b ± √(b² - 4ac)) / 2a, for ax² + bx + c = 0 |
| Slope of a line | m = (y² - y¹) / (x² - x¹) |
| Slope-intercept form | y = mx + b |
| Point-slope form | y - y¹ = m(x - x¹) |
| Difference of squares | a² - b² = (a + b)(a - b) |
| Perfect square trinomial | (a ± b)² = a² ± 2ab + b² |
| Exponent rules | am·an = am+n, (am)n = amn, a0 = 1 |
| Logarithm identity | logb(x) = y means by = x |
Worked example: solve 2x² + 3x - 2 = 0. Here a=2, b=3, c=-2. Plug into the quadratic formula: x = (-3 ± √(9 + 16)) / 4 = (-3 ± 5) / 4, giving x = 0.5 or x = -2.
Shapes & Space
| Shape | Area | Perimeter / Circumference |
|---|---|---|
| Rectangle | A = lw | P = 2(l + w) |
| Triangle | A = ½bh | P = a + b + c |
| Circle | A = πr² | C = 2πr |
| Trapezoid | A = ½(b¹ + b²)h | - |
| Solid | Volume | Surface Area |
|---|---|---|
| Rectangular prism | V = lwh | SA = 2(lw + lh + wh) |
| Cylinder | V = πr²h | SA = 2πrh + 2πr² |
| Sphere | V = &frac43;πr³ | SA = 4πr² |
| Cone | V = ⅓πr²h | - |
Pythagorean theorem: for a right triangle with legs a, b and hypotenuse c, a² + b² = c².
Angles
| Ratio | Definition (right triangle) |
|---|---|
| Sine | sin(θ) = opposite / hypotenuse |
| Cosine | cos(θ) = adjacent / hypotenuse |
| Tangent | tan(θ) = opposite / adjacent |
| Pythagorean identity | sin²(θ) + cos²(θ) = 1 |
| Law of sines | a/sin(A) = b/sin(B) = c/sin(C) |
| Law of cosines | c² = a² + b² - 2ab·cos(C) |
Memory trick: SOH-CAH-TOA - Sine = Opposite/Hypotenuse, Cosine = Adjacent/Hypotenuse, Tangent = Opposite/Adjacent.
Change & Accumulation
| Rule | Formula |
|---|---|
| Power rule (derivative) | d/dx[xn] = nxn-1 |
| Product rule | d/dx[fg] = f'g + fg' |
| Quotient rule | d/dx[f/g] = (f'g - fg') / g² |
| Chain rule | d/dx[f(g(x))] = f'(g(x))·g'(x) |
| Power rule (integral) | ∫xndx = xn+1/(n+1) + C |
| Derivative of sin/cos | d/dx[sin x] = cos x, d/dx[cos x] = -sin x |
Strategy
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