It is known that in square ABCD, e is the point above AB, passing through e as EF ⊥ AB, intersecting BD with F, and G is the midpoint of DF, connecting eg and CG

It is known that in square ABCD, e is the point above AB, passing through e as EF ⊥ AB, intersecting BD with F, and G is the midpoint of DF, connecting eg and CG

Connect AG, then take AE midpoint H
GH is the median line of trapezoidal efad
So GH ‖ ad, then EHG is 90 degrees
GH obviously divides AE vertically, so Ag = eg, and then uses congruence to find Ag = CG