∫∫ s (x + y + Z) ds, where s is the upper hemisphere, z = √ a ^ 2-x ^ 2-y ^ 2 Detailed point, this is a class of surface integral problem

∫∫ s (x + y + Z) ds, where s is the upper hemisphere, z = √ a ^ 2-x ^ 2-y ^ 2 Detailed point, this is a class of surface integral problem

Firstly, the integral surface is symmetric with respect to xoz and YOZ planes, and the integrand (x + y) is an odd function with respect to X and Y respectively, so ∫ (x + y) = 0, the original integral = ∫ (ZDS), and (Z'x) ^ 2 + (z'y) ^ 2 + 1 = x ^ 2 / Z ^ 2 + y ^ 2 / Z ^ 2 + 1 = a ^ 2 / Z ^ 2, so the integral = ∫ (azdxdy / z = a ∫ (DXDY = π a ^ 3)