Let b (0 0,0 0) c be (10,0) and a be (3.6,4.8) p (m, 2.4) Q(m, 0).

With the same slope k of QR and AB coordinates, and k=3/4, the coordinate of R can be obtained.

R is (n, 4/3(n-m)). After doing R, BC and S intersect vertically, and n=3.6+0.64m passes through a similar triangle, so R.

The following is simple, divided into three situations, according to the coordinates of the distance, in the analysis.