Using the invariance property established in the preceding problem, express the product of inertia Ixy of an area A with respect to a pair of rectangular axes through O in terms of the moments of inertia Ix and Iy of A and the principal moments of inertia Imin and Imax of A about O. Use the formula obtained to calculate the product of inertia Ixy of the 76 × 51 × 6.4-mm angle cross section shown in Fig. 9.13B knowing that its maximum moment of inertia is 524 × 103 mm4.