

Online Geometry Problem 776: Triangle, Isogonal lines, Congruent angles,
Perpendicular, Concyclic points, Circle, Center,
Midpoint. Level: High School, College,
Mathematics Education

The figure below shows a triangle ABC with
angle ABD = angle EBC (isogonal lines). DF and EH are perpendicular to AB, DG and EM are
perpendicular to BC. Prove that F, H, G, M lie on a circle (concyclic
points) whose center O is the midpoint of DE.







