The length of 1 quadrilateral ABCD is twice the width. Because m is the midpoint of AD, AM = DM Because AB=AM, Angle AMB= Angle ABM Because angles A and D are 90 degrees, Angle AMB=45 degrees; Therefore, the angle BMC = 90; Because PEMF's quadrilateral pemf is rectangular.

When p moves to the midpoint of BC. Because the angle EPF = 90°

Hope to adopt