If the coordinates of the points `A,B,C,D be 91,2,3),(4,5,7),(-4,3,-6) and (2,9,2)` respectively the

If the coordinates of the points `A,B,C,D be 91,2,3),(4,5,7),(-4,3,-6) and (2,9,2)` respectively then find the angle between AB and CD.