Infographic Geometry Problem 922: Circle, Tangent Lines, Tangency Point, Chord, Secant, Harmonic Mean. Level: High School, College, Mathematics Education

PD and PE are tangent to circle O (figure below) and PAC is a secant that intersects chord DE at C. Prove that PC is the harmonic mean of PA and PB:
This entry contributed by Ajit Athle.