Online Geometry
Problem 680: Concentric Circles, Radii, Chords, Perpendicular, Metric Relations. Level: High School, College,
Mathematics Education

The figure shows two concentric circles with radii R and r. A chord AB
of the outer circle meets the inner circle at C and D, respectively, CE
is perpendicular to AB. If AC = a, CB = b, and CE = c, prove that
.