Alternate Interior Angles


When two lines are crossed by another line (Transversal):

Alternate Interior Angles are a pair of angles on the inner side of each of those 2 lines but on opposite sides of the transversal.

Alternate Interior Angles

In this example, these are two pairs of Alternate Interior Angles:

c and e


d and f

How To remember:

The angle pairs are on Alternate sides of the Transversal, and they are on the Interior of the two crossed lines.

Parallel Lines

When the two lines being crossed are Parallel Lines the Alternate Interior Angles are equal.

Learn More

Alternate Exterior Angles

Consecutive Interior Angles

Vertical Angles

Angles of Elevation & Depression

Geometry Index