Angles of parallel lines 2  Angles and intersecting lines  Geometry  Khan Academy  Summary and Q&A
TL;DR
Corresponding angles formed by parallel lines and transversals are always equivalent.
Questions & Answers
Q: What are corresponding angles?
Corresponding angles are pairs of angles that are in the same relative positions when a transversal intersects two parallel lines. They are always equivalent in measure.
Q: How can we determine the measure of an unknown angle in a diagram with parallel lines and a transversal?
If we know the measure of a corresponding angle, we can determine the measure of an unknown angle by using the fact that corresponding angles are always equivalent. By applying the concept of supplementary angles, we can set up an equation and solve for the unknown angle.
Q: How can we determine if two lines are parallel using angle measurements?
If we have a pair of intersecting lines with given angle measurements, we can determine if the lines are parallel by checking if the corresponding angles are equivalent. If they are not, then the lines are not parallel.
Q: Do the measures of corresponding angles only apply to angles on the same transversal?
No, the measures of corresponding angles apply to angles formed by any transversal that intersects parallel lines. The angles in different parallel lines will still be equivalent if they are in the same relative positions.
Summary & Key Takeaways

Parallel lines will never intersect and are in the same plane.

When a transversal intersects parallel lines, corresponding angles formed by the transversal and the parallel lines are always equivalent.

Supplementary angles are formed when the measures of two angles add up to 180 degrees.