Problem 211. 60 Degree Triangle, Equilateral triangles, Areas. Elearning.
In the figure below, given a triangle
ABC of area S, the measure of the angle ABC is 60 degree and
ABD, BCE, and ACF are equilateral triangles of areas Sc, Sa, and Sb respectively. Prove that
(1) Sb = Sa + Sc - S, and (2)