A trapezoid is any four-sided figure that has at least one pair of parallel sides. Pictured below is trapezoid ABCD whose side AD is parallel to side BC. Line m is the perpendicular bisector of side AD, with midpoint at E. Line m also bisects side BC with midpoint at F. a) Explain why line m must also be perpendicular to side BC.
b) What rigid motion could be used to show that AB=CD? Explain how the mapping would work.