**If Two Parallel Lines Are Cut By A Transversal**. Alternate exterior angles formed when two parallel lines are cut across by the same transversal line, are said to be congruent. Prove that if two parallel lines are intersected by a transversal, then the bisectors of the interior angles on the.

If two parallel lines are cut by a transversal, then (i) each pair of alternate angles are equal; The transversal can either cut the parallel lines diagonally or at perpendicular angles. Alternate interior angles formed by a transversal and parallel lines are equal.