In summary, ∠1, ∠3, ∠5, ∠7 are congruent and ∠2, ∠4, ∠6, ∠8 are also congruent. Exterior angles on the same side of the transversal are supplementary.Consecutive interior angles are supplementary.Corresponding angles on the same side of the transversal are congruent.Alternate interior angles are congruent.Alternating exterior angles are congruent.Several relationships exist among these angles. ∠1 and ∠8, ∠2 and ∠7 are pairs of exterior angles on the same side of the transversal.∠3 and ∠6, ∠4 and ∠5 are pairs of consecutive interior angles.∠1 and ∠5, ∠2 and ∠6, ∠3 and ∠7, ∠4 and ∠8 are called corresponding angles.∠3, ∠4, ∠5, ∠6 are called interior angles.∠1, ∠2, ∠7, ∠8 are called exterior angles.Parallel lines m and n are cut by transversal l, above, forming angles 1–8. When 2 lines are cut (intersected) by a third line, called a transversal, 8 angles are formed. Transversals of parallel lines and their angles You can also place arrows on the lines, m and n, as in the figure above, to show they are parallel. The symbol to show parallel lines is "//". Line segments and rays that are parts of parallel lines are also parallel. Parallel lines are lines in the same plane that do not intersect. Home / geometry / line / parallel lines Parallel lines