Angle Vocabulary

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Ray

A part of a line with a starting point but no end point. It continues on forever in one direction.

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Vertex

Common point of two rays or line segments

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Acute Angle

An angle that measures greater than 0 degrees and less than 90 degrees

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Right Angle

An angle that measures exactly 90 degrees. Usually indicated with a box in the corner.

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Obtuse Angle

An angle that measures greater than 90 degrees and less than 180 degrees.

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Straight Angle

An angle that measures 180 degrees

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Reflex Angle

An angle that measures greater than 180 degrees and less than 360

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Adjacent Angles

two angles that share a common ray or side and a common vertex

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Vertical Angles

Pairs of opposite angles formed when 2 lines intersect.

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Complementary Angles

two angles whose measure add up to 90 degrees