# Angles on parallel lines

- Author:
- Mr E. Bissoon

- Topic:
- Angles

## Angles on parallel lines.

C.I.A. - This is not the Central Intelligence Agency! This acronym will help you to understand angles on parallel lines.
C - corresponding angles
I - Interior angles (or supplementary angles)
A - Alternate angles
Take a look at the graphic below.
Corresonding angles are marked in green.
Interior angles are marked in red.
Alternate angles are marked in blue.
Corresponding angles are always equal (on a parallel line).
Alternate angles are always equal (on a parallel line)
Interior angles (on a parallel line) always add up to 180