# 11 Angles

There are $360\textdegree$ (degrees) in a complete revolution (i.e. a full circle)

There are $180\textdegree$ in half a revolution (i.e. a straight angle, aka straight angle)

There are $90\textdegree$ in a quarter revolution (i.e. 2 lines perpendicular, aka a right angle). This has a special symbol:

Angles between $0\textdegree$ and $90\textdegree$ are called acute angles.

Angles between $90\textdegree$ and $180\textdegree$ are called obtuse angles.

Angles between $180\textdegree$ and $360\textdegree$ are called reflex angles.

When determining whether an angle is acute/obtuse/reflex, the position of the angle isn’t important, only the size. It does depend on which angle you’re talking about though, because the opposite side of an acute angle is going to be a reflex angle!