We measure the size of an angle using degrees.

Acute Angles

An acute angle is an angle measuring between 0 and 90 degrees.

Obtuse Angles

An obtuse angle is an angle measuring between 90 and 180 degrees.

Right Angles

A right angle is an angle measuring 90 degrees. Two lines or line segments that meet at a right angle are said to be perpendicular. Note that any two right angles are supplementary angles (a right angle is its own angle supplement).

Complementary Angles

Two angles are called complementary angles if the sum of their degree measurements equals 90 degrees. One of the complementary angles is said to be the complement of the other.

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