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Hypotenuse

longest side in a right triangle; opposite the right angle

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Scalene Triangle

triangle with no sides equal in length

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Line Segment

part of a line with two endpoints

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Vertex

point where two rays meet

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Perpendicular Lines

lines that intersect to form four right angles

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Quadrilateral

4-sided polygon

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Equilateral Triangle

triangle with all sides equal in length

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Diagonal

connects two non-consecutive vertices

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Line

a collection of points extending forever in opposite directions

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Point

an exact location in space

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Ray

contains an endpoint and extends forever in the opposite direction

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Parallel Lines

two lines that never intersect and are always the same distance apart

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Right Triangle

a triangle that contains a right angle

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Isosceles Triangle

a triangle with two sides equal in length

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Legs

the two sides of a right triangle that meet to form the right angle

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Square

a quadrilateral with 4 equal sides and 4 right angles

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Rectangle

a quadrilateral with 4 right angles and opposite sides are parallel and equal in length

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Right angle

an angle that is 90 degrees

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Trapezoid

a quadrilateral with one pair of parallel sides

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Angle

two rays with the same endpoint

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Rhombus

a quadrilateral with 4 equal sides and opposite angles equal

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Complementary angles

two angles whose sum is 90 degrees

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Supplementary angles

two angles whose sum is 180 degrees

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Adjacent angles

two angles that share a vertex and a common side, but have no common interior points

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Obtuse angles

angles whose measure is greater than 90 degrees and is less than 180 degrees

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Straight angles

an angle whose measure is 180 degrees

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Vertical angles

two nonadjacent angles formed by two intersecting lines

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Transversal

a line that cuts across a set of lines or the sides of a plane figure

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Symmetric

a geometric figure or graph consisting of two parts that are congruent to each other

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Skew lines

lines in three dimensional space that do not intersect and are not parallel

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Diameter

a line segment between two points on a circle or sphere which passes through the center

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Radius

a line segment between the center and a point on the circle or sphere

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Circumference

the distance around the outside of a circle

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Plane

a flat surface that can extend forever in length and width, but has no thickness

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Coplanar

points or lines that all lie in the same plane

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Congruent

planar figures or solid shapes that have the same shape and size

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Alternate interior angles

either pair of interior angles lying on opposite sides of the transversal

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Alternate exterior angles

either pair of exterior angles lying on opposite sides of the transversal

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Corresponding angles

two angles which occupy the same position, such as angles 1 and 5

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Acute angle

an angle whose measure is less than 90 degrees

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parallelogram

a 4 sided polygon with both pairs of opposite sides equal and opposite angles equal

### Flickr Creative Commons Images

Some images used in this set are licensed under the Creative Commons through Flickr.com. Click to see the original works with their full license.