In Rt△ABC, ∠ ACB = 90, BC=30, AB = 50. Point P is any point on the side of AB, and the straight line PE⊥AB intersects with the side of AC or BC. Point m is on line AP, point n is on line BP, EM=EN, SIN ∠ EMP =. ?

(1) As shown in figure 10, when point E coincides with point C, find the length of CM; ?

(2) As shown in figure 1 1, when point E is on the side of AC, and point E does not coincide with point A and point C, let AP=x and BN=y, find the functional relationship of Y about X, and write the definition domain of the function; ?

(3) If △ AME ∽△ENB (vertices A, M and E of △ AME correspond to vertices E, N and B of △ eNB respectively), find the length of AP.