It is equal ..you must prove that the quadrilateral GEHF is a rhombus....use the midle points it is easy.
A quadrilateral ABCD with mAB=mCD, where m means measure or length. mAD < mBC. E is the middle point of AD. F is the middle point of BC. G is the middle point of BD, H is the middle point of AC. Prove of disprove that angle of GEF must egual angle FEH. The points are below.
--------------A----- E ------D
-------------G
B--------------------- H
------------------F
--------------------------------------C