Triangle CDA is the image of triangle ABC after a 180° rotation around the midpoint of segment AC. Triangle ECB is the image of triangle ABC after a 180° rotation around the midpoint of segment BC. Part A: Explain why ABCD and ABEC are parallelograms.

Part B: Identify at least two pairs of congruent angles in the figure and explain how you know they are congruent.

Part C: Explain how to use what you know about the sum of the angles in a triangle to figure out the sum of the angles of quadrilateral ABED.