Integrate $f(x,y) = \sqrt{4-x^2-y^2}$ inside circle with radius 2 and center $(2,0)$

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An exercise asks to integrate

$$f(x,y) = \sqrt{4-x^2-y^2}$$

inside circle with radius 2 and center $(2,0)$.

When I set up the double integral I get

$$\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \int_{0}^{4cos(\theta)} \sqrt{4-r^2} r dr d\theta$$

Is that the correct way to set up the integral?

Should I really evaluate that as

$$ - \frac{1}{2} \int_{\frac{-\pi}{2}}^{\frac{\pi}{2}} \int_{0}^{4-16cos^2(\theta)} u^{1/2} du d\theta = - \frac{1}{3} \int_{\frac{-\pi}{2}}^{\frac{\pi}{2}} u^{3/2}\bigg|_{0}^{4-16cos^2(\theta)} d\theta = \cdots $$

which seems like a dead-end?