Let the vertices A and C of a right triangle ABC be on the arc with center B and radius 20. A semicircle with diameter [AB] is drawn to the inner region of the arc. The tangent from C to the semicircle touches the semicircle at D other than B. Let CD intersect the arc at F. What is ∣FD∣?<spanclass=′latex−bold′>(A)</span> 1<spanclass=′latex−bold′>(B)</span> 25<spanclass=′latex−bold′>(C)</span> 3<spanclass=′latex−bold′>(D)</span> 4<spanclass=′latex−bold′>(E)</span> 5 geometrygeometric transformationreflectionPythagorean Theorem