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# ShapesEdit

## CirclesEdit

$Area = \pi r^2$

$Circumference = 2$π$r$

$r = 2/d$ or $d = 2r$
where r = radius, d = diameter, and π = \pi (3.14..).

## SquaresEdit

$Area = l^2$

$Area = \frac{d^2}{2}$

Where $l$ is the length of a side, and $d$ is the diagonal.

## RhombusEdit

$Area = \frac{1}{2} \cdot d $$1$$ d$$2$

Where d are the diagonals of the rhombus.

## RectanglesEdit

$Area = lw$

$Perimeter = 2(l + w)$

Where $l$ is the length of a side, and $w$ is the width of a side.

## TrianglesEdit

Note* All angles of a triangle always add to 180, meaning solving for an angle can be done by: $a + b + c - 180$ where $a$,$b$, and $c$ are angles of the triangle.

### Trigonometric RatiosEdit

$sin($°$) = \frac{opp}{hyp}$

$cos($°$) = \frac{adj}{hyp}$

$tan($°$) = \frac{opp}{adj}$

### Area / OtherEdit

$Area = \frac{1}{2}bh$ Where $b$ is the base, and $h$ is the height of the triangle.

The following formulas are only true for right angle triangles:

$A^2 + B^2 = C^2$ Where each letter indicates a different side length

The following formula is only true for a equilateral triangle:

$Area = \frac{s^2}{\sqrt 3\cdot4}$

$a + b < c$

#### Sin LawEdit

For any you may use sin law, or cos law.

$\frac{a}{sin(A)} = \frac{b}{sin(B)} = \frac{c}{sin(C)}$

or

$\frac{sin(A)}{a} = \frac{sin(B)}{b} = \frac{sin(C)}{c}$

#### Cos LawEdit

$a^2 = b^2 + c^2 - 2bccost(A)$

or

$cos(A) = \frac{b^2 + c^2 - a^2}{2bc}$

# OtherEdit

$ax^2 + bx + c = 0$

If this is not true, you may follow the formula:$x = -b$±$\sqrt \frac{b^2 - 4ac}{2a}$

## CombinationsEdit

a Combination is used when the 'order' of a

Combinations are defined by nCr
$nCr = \frac{n!}{r!(n-r)!}$

## PermutationsEdit

A Permutation is an arrangement of a set. Used when the order of the set matters.

Permutations are defined by nPr.

Formula: $nPr = \frac{n!}{(n-r)!}$