Show that if the angular momentum of a body is determined with respect to an arbitrary poi...

Show that if the angular momentum of a body is determined with respect to an arbitrary point A, then HA can be expressed by Eq. 21-9. This requires substituting ρA = ρG + ρG/A into Eq. 21-6 and expanding, noting that ∫ρG dm = 0 by definition of the mass center and vG = vA + ω⨯ρG/A.