Types of angle
There are 360掳 in a full turn, 180掳 in a half turn and 90掳 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.
\(c = 90 - 20 = 70^\circ\)
There are three different types of angle.
An acute angle is an angle less than 90掳.
An obtuse angle is an angle between 90掳 and 180掳.
A reflex angle is an angle between 180掳 and 360掳.