a) Show that
∫ddqqμf(q2)=0,(14.52)∫ddqqμqνf(q2)=C2gμν∫ddqq2f(q2),(14.53)
and evaluate the constant C2 in terms of d. Hint: use Lorentz symmetry to argue for the general structure, and evaluate C2 by contracting with gμν.
b) Similarly evaluate ∫ddqqμqνqρqσf(q2).