# Angles at a point and on a straight line

## Angles at a point

around a point add up to 360°. This fact can be used to calculate missing angles.

### Example

Calculate angle $$a$$.

$a = 360^\circ - 60^\circ - 95^\circ - 105^\circ = 100^\circ$

## Angles on a straight line

Angles on a straight line add up to 180°. This fact can also be used to calculate angles.

### Example

Calculate the angles $$b$$ and $$c$$.

$b = 180^\circ - 30^\circ = 150^\circ$

$c = 180^\circ - 150^\circ = 30^\circ$

$$c$$ and $$30^\circ$$ are called vertically opposite angles.

Vertically opposite angles are equal.