Alternate Interior Angles
When two lines are crossed by another line (called the Transversal): The pairs of angles on opposite sides of the transversal but inside the two lines are called Alternate Interior Angles. In this example, these are Alternate Interior Angles:
(To help you remember: the angle pairs are on "Alternate" sides of the Transversal, and they are on the "Interior" of the two crossed lines) |
Parallel LinesIf the two lines being crossed are Parallel Lines, then the Alternate Interior Angles are equal. (Click on "Alternate Interior Angles" to have them highlighted for you.) |