(a) Show that the angular momentum HB of a rigid body about point HB can be obtained by adding to the angular momentum HA of that body about point A the vector product of the vector rA/B drawn from B to A and the linear momentum mv of the body: HB = HA + rA/B × mv

(b) Further show that when a rigid body rotates about a fixed axis, its angular momentum is the same about any two points A and B located on the fixed axis (HA = HB) if, and only if, the mass center G of the body is located on the fixed axis.