Types of angle
There are 360° in a full turn, 180° in a half turn and 90° in a quarter turn. A quarter turn is called a right angle.
A right angle is shown by a small square. This fact can be used to calculate unknown angles.
Example
Calculate angle \(c\).
A right angle is shown.
\(c = 90^\circ - 20^\circ = 70^\circ\)
There are three different types of angle.
An acute angle is an angle less than 90°.
An obtuse angle is an angle between 90° and 180°.
A reflex angle is an angle between 180° and 360°.