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intersection

point where two or more lines cross

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equilateral

triangle with 3 equal sides

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corresponding

angles in the same position at different points of a figure

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protractor

tool used to draw or measure angles

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ray

set of points that is part of a line; has an endpoint and extends

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vertex

common point to both sides of an angle

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acute

angle smaller than 90 degrees

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vertical

pairs of opposite angles; have the same measure

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right triangle

triangle with a 90 degree angle

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supplementary

two angles whose sum of their measures is 180 degrees

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straight

angle measuring 180 degrees

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isosceles

two of the sides in a triangle are the same

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equiangular

triangle with 3 equal angles, measuring 60 degrees

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interior

angle within a polygon

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acute triangle

a triangle with all 3 angles less than 90 degrees

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obtuse triangle

triangle with one obtuse angle

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obtuse

larger than 90 degrees

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adjacent

angle that shares a vertex and a common side with another angle

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complementary

two angles whose sum of their measures is 90 degrees

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exterior

angle formed by extending one side of a polygon at a vertex

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scalene

all the sides of a triangle have different lengths

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congruent

having the same size and shape

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similar

figures that have the same shape but not the same size

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quadrilaterals

polygons with 4 sides and 4 angles

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diagonal

a line that connects two vertices that are not next to each other

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regular polygon

polygon with all equal sides and angles

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