Geometry Problem 1359: Triangle, Circumcircle, Congruent Angles, Midpoints.
Proposition
A triangle ABC is inscribed in a circle and a point D is on the arc AB.
Angles DEC and DFB are congruent, G is the midpoint of BC and H is the
midpoint of EF. (See the figure below). Prove that angles DHG and DEC are congruent