*Postulate 11 (Parallel Postulate):* If two parallel lines are cut by a transversal, then the corresponding angles are equal (Figure 1

**Figure 1**Corresponding angles are equal when two parallel lines are cut by a transversal.

This postulate says that if *l* // *m*, then

*m*∠1 =*m*∠5

*m*∠2 =*m*∠6

*m*∠3 =*m*∠7

*m*∠4 =*m*∠8