When a transversal cuts two parallel lines, corresponding angles are equal and alternate interior angles are equal. Same-side interior angles are supplementary. Parallel-line facts as a set are in parallel and perpendicular lines.
Match the corners
Corresponding angles sit in the same corner of each intersection. Alternate interior angles sit between the parallels, on opposite sides of the transversal. If the lines are not parallel, none of those equalities holds.
Complementary and supplementary sums are in complementary and supplementary angles. Basic angle vocabulary is in lines and angles. The short list is in ACT Math formulas.
The bottom line
Parallels plus a transversal: corresponding equal, alternate interior equal, same-side interior 180.
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