A,B,C are collinear with B betweeen A and C. K1 is the circle with diameter AB, and K2 is the circle with diameter BC. Another circle touches AC at B and meets K1 again at P and K2 again at Q. The line PQ meets K1 again at R and K2 again at S. Show that the lines AR and CS meet on the perpendicular to AC at B. geometryparallelogrampower of a pointradical axisgeometry unsolved