# 1.1: Angles

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- 2631

## What’s the deal with angles anyway?

**Degree.** One-three-hundred-and-sixtieth of the circumference of a circle. It is also the unit by which we measure angles.

**Angle. **This is the space between two intersecting lines.

**Complementary angles.** These are two angles whose sum equals 90 degrees.

**Supplementary angles. **These are two angles whose sum equals 180 degrees.

**Acute angle.** An angle that is less than 90 degrees.

**Obtuse angle.** An angle that is greater than 90 degrees.

**Similar angles. **It is possible for triangles to each have different sized sides but share the same sized angles. These are called similar angles.

**Right angle. **This is an angle that is 90 degrees.