Online Geometry Problem 797: Parallelogram, Angle Bisector, Isosceles and Similar Triangles. Level: High School,
SAT Prep, College,
Mathematics Education

The figure below shows a parallelogram ABCD,
AE is the bisector of angle BAD. If AE and DC meet at F, prove that
triangles ABE, ECF, and ADF are isosceles and similar.