In figure AB$\parallel PQ \parallel CD$ Prove that $\frac 1 x + \frac 1 y = \frac 1 z$
Equilateral triangles APB, BQC and ASC are described on each side of a right-angled triangle ABC, right angled at B. Then prove that ar($\triangle$APB)+ar($\triangle$BQC)=ar($\triangle$ASC).