Online Geometry Problems, High School, College

Online Geometry Problem 470. Triangle, Parallel, Parallelogram, Area, Similarity

The figure below shows a triangle ABC of area S, DE parallel to AC and EF parallel to AB. If S1, S2, and S3 are the areas of triangle DBE, triangle CEF, and parallelogram ADEF respectively, prove that (1) Formula to prove 1, (2) Formula to prove 2.

Problem 470: Triangle Similarity Area