###
intersection

point where two or more lines cross

###
equilateral

triangle with 3 equal sides

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corresponding

angles in the same position at different points of a figure

###
protractor

tool used to draw or measure angles

###
ray

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

###
vertex

common point to both sides of an angle

###
acute

angle smaller than 90 degrees

###
vertical

pairs of opposite angles; have the same measure

###
right triangle

triangle with a 90 degree angle

###
supplementary

two angles whose sum of their measures is 180 degrees

###
straight

angle measuring 180 degrees

###
isosceles

two of the sides in a triangle are the same

###
equiangular

triangle with 3 equal angles, measuring 60 degrees

###
interior

angle within a polygon

###
acute triangle

a triangle with all 3 angles less than 90 degrees

###
obtuse triangle

triangle with one obtuse angle

###
obtuse

larger than 90 degrees

###
adjacent

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

###
complementary

two angles whose sum of their measures is 90 degrees

###
exterior

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

###
scalene

all the sides of a triangle have different lengths

###
congruent

having the same size and shape

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similar

figures that have the same shape but not the same size

###
quadrilaterals

polygons with 4 sides and 4 angles

###
diagonal

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

###
regular polygon

polygon with all equal sides and angles

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