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acute angle

An angle less than 90 degrees

right angle

an angle that measures 90 degrees

obtuse angle

An angle more than 90 degrees

complementary angles

two angles whose measures have a sum of 90 degrees

supplementary angles

two angles whose measures have a sum of 180 degrees


Sides are congruent, angles are congruent

vertical angles

a pair of opposite congruent angles formed by intersecting lines

adjacent angles

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

alternate interior pair

angles which are on opposite sides of the transversal and inside of the parallel lines

corresponding angles

are angles which are in a similar position in relation to the transversal and the line that it intersects

parallel lines

lines that never intersect

perpendicular lines

Two lines that intersect to form right angles

equilateral triangle

a triangle with three congruent sides

isosceles triangle

a triangle with two congruent sides

scalene triangle

a triangle with no congruent sides

acute triangle

A triangle with three acute angles

obtuse triangle

a triangle with one obtuse angle

right triangle

a triangle with 1 right angle


a parallelogram with 4 congruent sides


a four-sided polygon


A quadrilateral with two pairs of parallel sides


a quadrilateral with exactly one pair of parallel sides


a parallelogram with four congruent sides and four right angles


A parallelogram with 4 right angles


a closed plane figure made up of line segments


a five-sided polygon


a six-sided polygon


a seven-sided polygon


an eight-sided polygon


a nine-sided polygon


a ten sided polygon

regular polygon

a polygon with congruent sides and angles

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