(1) makes the vertical line of CB pass through D, and the vertical foot is F. Because the angle B is 45 degrees, δ△DFB is isosceles δ, δDB = 1, so DF=FB=0.707. (2) Because AB=4 times the radical number 2 and AC=CB=4, the sum of CD = (4-0.707) * (4-0.707)+0.707 * 0.707 is equal to 3.368 (3), which proves that △AEC and △CFD are similar, so AC: CD = CE:.