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acute angle

An angle less than 90 degrees

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right angle

an angle that measures 90 degrees

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obtuse angle

An angle more than 90 degrees

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complementary angles

two angles whose measures have a sum of 90 degrees

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supplementary angles

two angles whose measures have a sum of 180 degrees

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congruent

Sides are congruent, angles are congruent

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vertical angles

a pair of opposite congruent angles formed by intersecting lines

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adjacent angles

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

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alternate interior pair

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

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corresponding angles

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

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parallel lines

lines that never intersect

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perpendicular lines

Two lines that intersect to form right angles

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equilateral triangle

a triangle with three congruent sides

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isosceles triangle

a triangle with two congruent sides

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scalene triangle

a triangle with no congruent sides

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acute triangle

A triangle with three acute angles

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obtuse triangle

a triangle with one obtuse angle

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right triangle

a triangle with 1 right angle

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rhombus

a parallelogram with 4 congruent sides

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quadrilateral

a four-sided polygon

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parallelogram

A quadrilateral with two pairs of parallel sides

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trapezoid

a quadrilateral with exactly one pair of parallel sides

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square

a parallelogram with four congruent sides and four right angles

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rectangle

A parallelogram with 4 right angles

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polygons

a closed plane figure made up of line segments

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pentagon

a five-sided polygon

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hexagon

a six-sided polygon

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heptagon

a seven-sided polygon

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octagon

an eight-sided polygon

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nonagon

a nine-sided polygon

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decagon

a ten sided polygon

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regular polygon

a polygon with congruent sides and angles

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