Today we learned how to find out if two lines are parallel. We do this by using the converse's to angle postulates. (a converse is a statement opposite to a hypothesis)

For example- You could write this statement in two ways, proving two different things;
1. If 2 lines are cut by a transversal so that the lines are parallel, then the corresponding angles are congruent.
OR
2. If two lines are cut by a transversal so that the corresponding angles are congruent, then the lines are parallel.
The first statement just states that corresponding angles are congruent, corresponding angles postulate.
The second statement is the converse of this, and states that the two lines are parallel. (corrospondign angles converse)

When trying to figure out if lines are parallel you have to look at the converses of normal angle postulates.