MHB Find the integral of this function

[kalvin]

Find the integral of the function $f(x,y) = \frac{1}{(x^2 + y^2 + 1)^{\frac{3}{2}}} $
over the closed ball $\overline{B(a, 2)}$(i.e disk with radius 2 centered at point a). Letting $a \rightarrow \infty$, show that:

$\int_{-\infty}^{\infty} \int_{-\infty}^{\infty}f(x,y) dydx = 2\pi$

 

[Opalg]

Find the integral of the function $f(x,y) = \frac{1}{(x^2 + y^2 + 1)^{\frac{3}{2}}} $
over the closed ball $\overline{B(a, 2)}$(i.e disk with radius 2 centered at point a). Letting $a \rightarrow \infty$, show that:

$\int_{-\infty}^{\infty} \int_{-\infty}^{\infty}f(x,y) dydx = 2\pi$

That wording cannot be correct: $a$ must surely be the radius of the disc, not its centre?