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### Area of a Parallelogram Theorem

The area of a parallelogram is the product of a base and its corresponding height.

A=b∗h

### Area of a Triangle Theorem

The area of a triangle is one half the product of a base and its corresponding height.

A=½∗b∗h

### Area of a Trapezoid Theorem

The area of a trapezoid is one half the product of the height and the sum of the lengths of its bases.

A=½∗h(b₁+b₂)

### Area of a Rhombus or a Kite Theorem

The area of a rhombus or a kite is one half the product of the lengths of its diagonals.

A=½∗d₁∗d₂

### Areas of Similar Polygons Theorem

If two polygons are similar with the lengths of corresponding sides in the ratio of a:b, then the ratio of their areas is a²:b².

### Circumference of a Circle Theorem

The circumference C of a circle is C=πd or C=2πr where d is the diameter and r is the radius of the circle.

C=πd or C=2πr

### Arc Length Corollary

In a circle, the ratio of the length of a given arc to the circumference is equal to the ratio of the measure of the arc to 360°.

(Arc length of AB/πd) = (mAB/360°)

### Area of a Sector Theorem

The ratio of the area of a sector of a circle to the whole circle (πr²) is equal to the ratio of the measure of the intercepted arc to 360°.

(Area of sector APB/πr²) = (mAB/360°)

### apothem (of the polygon)

the distance from the center to any side of the polygon

is the height to the base of an isosceles triangle that has two radii as legs

### central angle (of a regular polygon)

any angle formed by two radii drawn to consecutive vertices of the polygon

### Area of a Regular Polygon Theorem

Area of a regular n-gon with side length s is half the product of the apothem a and the perimeter P.

A=½∗a∗P or A=½∗a∗n∗s

### probability (of an event)

measure of the likelihood that the event will occur

a number between 0 & 1, inclusive

can be expressed as a fraction, decimal, or percent

written P(A)