The diagonals bisect each other. The exterior angles of a rectangle are each 90°. Parallelogram. A parallelogram has two pairs of equal sides. It has two pairs of equal angles.

As we know, the exterior angle plus the interior angle adds up to 180°, so the missing angles moving clockwise from the top are: 180 – 71.4 = 108.6° 180 – 56.4 = 123.6° ...