Two concentric circles of radius R and r, with R>r are both intersected by the same secant line. The points of intersection, in order, are A,B,C,D.
Prove AC*CD is constant.
Working with Geometer's Sketchpad with two concentric circles, at various sizes, given the constant set of circles, moving the secant line up and down leaves the product of those lengths constant.

Posted by Charlie
on 20180215 09:29:37 