Definition:Angle/Types

Definition

Angles can be divided into categories:

Zero Angle

The zero angle is an angle the measure of which is $0$ regardless of the unit of measurement.

Acute Angle

An acute angle is an angle which has a measure between that of a right angle and that of a zero angle.

Right Angle

A right angle is an angle that is equal to half of a straight angle.

Obtuse Angle

An obtuse angle is an angle which has a measurement between those of a right angle and a straight angle.

Straight Angle

A straight angle is defined to be the angle formed by the two parts of a straight line from a point on that line.

Reflex Angle

A reflex angle is an angle which has a measure between that of a straight angle and that of a full angle.

Full Angle

A full angle is an angle equivalent to one full rotation.

It is possible to consider angles outside the range $\closedint {0 \degrees} {360 \degrees}$, that is, $\closedint 0 {2 \pi}$.

However, in geometric contexts it is usually preferable to convert these to angles inside this range by adding or subtracting multiples of a full angle.