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line

is perfectly straight and extends forever in both directions

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plane

is a perfectly flat surface that extends forever in all directions

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segment

is the part of a line between two points

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ray

is part of a line that starts at one point and extends forever in one direction

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angle

is formed by two rays with a common end-point called the vertex.

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right angle

an angle that measures 90 degrees

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acute angle

an angle that measures more than zero but less than 90 degrees

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obtuse angle

an angle that measures more than 90 degrees, but less than 180 degrees

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complementary angles

two angles whose measures add to 90 degrees

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supplementary angles

two angles whose measures add up to 180 degrees

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congruent figures

figures that have the same shape and same size

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vertical angles

a pair of opposite congruent angles formed by intersecting lines

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Triangle Sum Theorem

states that the measures of the angles in a triangle add up to 180 degrees

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acute triangle

has 3 acute angles

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right triangle

has one right angle

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obtuse triangle

has one obtuse angle

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equilateral triangle

has three congruent sides and angles

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isosceles triangle

has at least two congruent sides and angles

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scalene triangle

has NO congruent sides or angles

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polygon

is a closed plane figure formed by three or more sides

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regular polygon

a polygon with congruent sides and angles

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trapezoid

a quadrilateral with exactly one pair of parallel sides

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paralellogram

a quadrilateral that has 2 pairs of parallel sides

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rectangle

a parallelogram with four right angles

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rhombus

a parallelogram with all side congruent

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square

a parallelogram with four right angles and four congruent sides

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