(1) Because the angle c is a right angle, the circumferential angle corresponding to the semicircle (or diameter) is a right angle; According to this definition, the distance from the midpoint m of the ladder to the point c is 1/2AB, that is, 2m.

(2) Because the length of MC is unchanged, the ladder begins to slide down to the overlap of A and C, and the distance traveled by the midpoint M of the ladder is 1/4, a circle with the center of C and the radius of 2m. ..