It's easier to convert to polar coordinates in the xz-plane: x = rcos(θ), z = rsin(θ). this gives int int int √x2 + z2dv = int int (1 - x2 - z2) √x2 + z2 da = int_0^(2pi)int_0^1 incorrect: your answer is incorrect. dr dθ = int_0^(2pi) dθ int_0^1 incorrect: your answer is incorrect. dr = 2π [ incorrect: your answer is incorrect. ]_0^1 = incorrect: your answer is incorrect.