## Vertically Opposite Angles

Table of Contents

## Vertically Opposite Angles Definition

Vertically Opposite Angles are the angles opposite each other when 2 lines cross

Vertical in this case means they share the same corner point (vertex), not the usual meaning of up-down.

*a* and *c* are vertically opposite angles. *b* and *d* are also vertically opposite angles.

The interesting thing here is that vertically opposite angles are equal:

*a* = c

*b* = *d*

(in fact they are congruent angles)

## Example

Find angles *a*, *b* and *c* below:

Because b° is vertically opposite 60°, it must also be 60°

So, *b* = 60°

A full circle is 360°, so that leaves 360° − 2×60° = 240°

Angles a and c are also vertically opposite angles, so must be equal, which means they are 120° each.

**Answer: **

*a* = 120°, *b* = 60° and *c* = 120°.