# Angle

An angle is defined as the amount of rotation between two rays. The point where the rays start is called the vertex. There are two systems for measuring angles in mathematics: degrees and radians. While the degree angle system is often used to introduce concepts in math, the radian system eventually becomes the preferred unit for measuring angles[1].

## Types of Angles

A perpendicular angle is equal to a quarter of a full rotation.

An acute angle is defined as an angle smaller than a perpendicular angle.

An obtuse angle is defined as an angle greater than a perpendicular angle.

## References

1. Radians Versus Degrees
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