Problem

Find the volume $V$ of the solid below the paraboloid $z=8-x^{2}-y^{2}$ and above the following region.
\[
R=\left\{(r, \theta): 1 \leq r \leq 2,-\frac{\pi}{2} \leq \theta \leq \frac{\pi}{2}\right\}
\]
Set up the double integral, in polar coordinates, that is used to find the volume.
(Type exact answers.)
Find the volume.
\[
\mathrm{V}=
\]
(Type an exact answer, using $\pi$ as needed.)

Answer

Expert–verified
Hide Steps
Answer

Evaluating this integral gives us the volume of the solid. The final answer is \(\boxed{\frac{33\pi}{4}}\)

Steps

Step 1 :We are given a solid below the paraboloid \(z=8-x^{2}-y^{2}\) and above the region \(R=\left\{(r, \theta): 1 \leq r \leq 2,-\frac{\pi}{2} \leq \theta \leq \frac{\pi}{2}\right\}\). We are asked to find the volume of this solid.

Step 2 :We can find the volume of the solid by setting up a double integral in polar coordinates. The limits of integration for r will be from 1 to 2, and for theta will be from -pi/2 to pi/2.

Step 3 :The function to be integrated will be the function for the paraboloid, converted to polar coordinates. In polar coordinates, x = rcos(theta) and y = rsin(theta), so the function becomes z = 8 - r^2.

Step 4 :The differential area element in polar coordinates is rdrdtheta, so the double integral becomes: \[\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \int_{1}^{2} (8 - r^2) r dr d\theta\]

Step 5 :Evaluating this integral gives us the volume of the solid. The final answer is \(\boxed{\frac{33\pi}{4}}\)

link_gpt