If two coplanar lines are cut by a transversal so that corresponding angles are congruent, then the lines are parallel
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Explanation:
This is due to the converse of the corresponding angles theorem.
Ignoring the "converse" part for now, the corresponding angles theorem says that if two lines are parallel, then the corresponding angles are congruent.
The converse swaps the order. The converse says that if two corresponding angles are congruent, then the lines are parallel.
Corresponding angles are the angles that are in the same configuration of the four-angle set up. For instance, both angles could be in the upper right corner for each X shape.
Check out the image below to see an example of what I mean.
