Point D is a turning point so the angular velocity at point D is zero.� You indicated that the angular acceleration at point D is also zero.� Zero angular acceleration indicates that the angular velocity for the portion of the motion that spans point D has not changed. Is it true that the angular velocity just prior to point D is the same as the angular velocity just after point D?�

The direction of the angular acceleration at a turning point is the same as the direction of the angular acceleration just before or just after the turning point.