# Vertically Opposite Angles

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

"Vertical" in this case means they

**share the same Vertex**(or corner point), not the usual meaning of up-down.
In this example, a° and b° are vertically opposite angles. The interesting thing here is that ## a° = b°(in fact they are congruent angles) |

Have a play with them yourself (click on "vertical angles"). Notice how the 4 angles are actually **two pairs** of "vertically opposite angles":

### Example: Find angles a°, b° and c° below:

Because b° is vertically opposite 40°, it must also be 40°

A full circle is 360°, so that leaves 360° − 2×40° = 280°

Angles a° and c° are also vertical angles, so must be equal, which means they are 140° each.

Answer: **a = 140°**,** b = 40° and c = 140°**.

Language Note: "Vertically Opposite Angles" are usually called Vertical Angles in the US