Consequently, angle D = angle F and angle G = angle E. Parallel Lines Cut by a Transversal When two parallel lines are cut by a transversal (i.e., a third line intersects the two parallel lines), a number of relationships exist between the resulting angles.

Motion pro chainsaw fuel cap• parallel lines • transversal • interior angles • exterior angles • alternate interior angles • alternate exterior angles • Identify the relationships of angles formed by two parallel lines and a transversal. • Identify the relationships of vertical, adjacent, complementary, and supplementary angles. • corresponding angles

Theorem: If three parallel lines cut congruent segments off a transversal then, they cut off congruent segments on every transversal. Corollary: A line that contains the midpoint of one of the sides of a triangle and is parallel to another side bisects the third side of the triangle.