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acute angle

an angle with a measure greater than 0 degrees and less than 90 degrees

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angle

two rays with a common endpoint

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angle bisector

A ray that divides an angle into two congruent angles.

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area

the number of square units needed to cover a flat surface

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circumference

distance around a circle

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collinear points

Points that lie on the same line.

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complementary angles

Two angles whose measures have the sum of 90 degrees

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congruent angles

Angles that have the same measure.

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congruent segments

Segments that have the same length

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coordinate

The number that corresponds to a point

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coplanar

figures in the same plane

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line

a series of points that extends in two opposite directions without end

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midpoint

a point that divides a segment into two congruent segments

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obtuse angle

An angle that measures more than 90 degrees but less than 180 degrees

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opposite rays

two collinear rays with the same endpoint

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parallel lines

lines in the same plane that never intersect

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parallel planes

planes that do not intersect.

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perimeter

The sum of the lengths of the sides of a polygon.

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perpendicular bisector

a segment, ray, line, or plane that is perpendicular to a segment at its midpoint

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perpendicular lines

Two lines that intersect to form right angles

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plane

A flat surface that goes on forever in all directions

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ray

part of a line with one endpoint

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right angle

an angle that measures 90 degrees

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segment

part of a line with two endpoints

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skew lines

lines that do not lie in the same plane

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straight angle

an angle whose measure is 180 degrees

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supplementary angles

two angles that add up to 180 degrees

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vertical angles

two angles whose sides form two pairs of opposite rays

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Midpoint Formula

M = [ ( x₂ + x₁) / 2, (y₂ + y₁) / 2 ]

To get your x-coordinate: Add the x's and divide by 2

To get your y-coordinate: Add the y's and divide by 2

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Distance formula

d = √[( x₂ - x₁)² + (y₂ - y₁)²]

It does not matter which point is labeled 1 and which is labeled 2

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Perimeter of a Rectangle

P = 2L+2W

where L = length and W = width

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Perimeter of a Square

P = 4s

where s = length of side

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Circumference of a Circle

C=2πr or C=πd

where r = radius and d = diameter and π = pi (approx. 3.14)

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Area of a Square

A = s²

where s = length of side

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Area of a Rectangle

A = L x W

where L=length and W = width

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Area of Circle

A=πr²

where r = radius and π = pi (approx. 3.14)

### Flickr Creative Commons Images

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