Which of the following equations does not represent a true statement?

Rewrite the following integral in spherical coordinates.

lora16 [44]

In cylindrical coordinates, we have $r^2=x^2+y^2$ , so that

$z = \pm \sqrt{2-r^2} = \pm \sqrt{2-x^2-y^2}$

correspond to the upper and lower halves of a sphere with radius $\sqrt2$ . In spherical coordinates, this sphere is $\rho=\sqrt2$ .

$1 \le r \le \sqrt2$ means our region is between two cylinders with radius 1 and $\sqrt2$ . In spherical coordinates, the inner cylinder has equation

$x^2+y^2 = 1 \implies \rho^2\cos^2(\theta) \sin^2(\phi) + \rho^2\sin^2(\theta) \sin^2(\phi) = \rho^2 \sin^2(\phi) = 1 \\\\ \implies \rho^2 = \csc^2(\phi) \\\\ \implies \rho = \csc(\phi)$

This cylinder meets the sphere when

$x^2 + y^2 + z^2 = 1 + z^2 = 2 \implies z^2 = 1 \\\\ \implies \rho^2 \cos^2(\phi) = 1 \\\\ \implies \rho^2 = \sec^2(\phi) \\\\ \implies \rho = \sec(\phi)$

which occurs at

$\csc(\phi) = \sec(\phi) \implies \tan(\phi) = 1 \implies \phi = \dfrac\pi4+n\pi$

where $n\in\Bbb Z$ . Then $\frac\pi4\le\phi\le\frac{3\pi}4$ .

The volume element transforms to

$dx\,dy\,dz = r\,dr\,d\theta\,dz = \rho^2 \sin(\phi) \, d\rho \, d\theta \, d\phi$

Putting everything together, we have

$\displaystyle \int_0^{2\pi} \int_1^{\sqrt2} \int_{-\sqrt{2-r^2}}^{\sqrt{2-r^2}} r \, dz \, dr \, d\theta = \boxed{\int_0^{2\pi} \int_{\pi/4}^{3\pi/4} \int_{\csc(\phi)}^{\sqrt2} \rho^2 \sin(\phi) \, d\rho \, d\phi \, d\theta} = \frac{4\pi}3$

4 0

2 years ago

The radius of a sphere and of a cylinder are the same. The diameter of the sphere and the height of the cylinder are also the sa

emmasim [6.3K]

First we have to know the formula of the volume f each of the solids,

V of sphere = 4/3 pi r^3
Volume of Cylinder = pi r^2(2r)=2pi r^3
Volume of cone = 1/3 pi r^2(r)=1/3 pi r^3

The surest and easiest way we can answer this is actually assigning values. We first assign values to r hence we would get the volume of the sphere and rest of the solids (cylinder and cone). You then compare your answers to that of the sphere, and you should get your answer.

4 0

3 years ago

2. True False 6(10 + 5) - 6.10 + 6.5 <img src="https://tex.z-dn.net/?f=10%20%2B%205%20-%206.10%20%2B%206.5%20%5Ctimes%206" id

Ostrovityanka [42]

Answer:

Step-by-step explanation:

$10 + 5 - 6.10 + 6.5 \times 6 \\$