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intersection

point where two or more lines cross

equilateral

triangle with 3 equal sides

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

right

a 90 degree 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

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