5.2.4.18 Various Problems on the Plane

In the bulk of the quadrangle \ (a b c d \) the diagonals intersect at point \ (m \), and \ (C m = d m \). Find the angle between the straight line \ (C D \) and the bisector of the angle \ (b A C \) if the angle \ (A B M = 78^{\ CIRC} \) is known.