Evaluate the surface integral. ∫∫s y2 ds s is the part of the sphere x2 + y2 + z2 = 100 that lies inside the cylinder x2 + y2 = 25 and above the xy-plane

Respuesta :

Parameterize the region in spherical coordinates using

[tex]\mathbf r(\theta,\varphi)=\begin{cases}x(\theta,\varphi)=10\cos\theta\sin\varphi\\y(\theta,\varphi)=10\sin\theta\sin\varphi\\z(\theta,\varphi)=10\cos\varphi\end{cases}[/tex]

with [tex]0\le\theta\le2\pi[/tex] and [tex]0\le\varphi\le\dfrac\pi3[/tex]. Then

[tex]\left\|\mathbf r_\theta\times\mathbf r_\varphi\right\|=\|\langle-100\cos\theta\sin^2\varphi,-100\sin\theta\sin^2\varphi,-100\sin\varphi\cos\varphi\rangle\|[/tex]
[tex]=100\sin\varphi[/tex]

Now the surface integral is

[tex]\displaystyle\iint_Sy^2\,\mathrm dS=\iint_Sy(\theta,\varphi)^2\left\|\mathbf r_\theta\times\mathbf r_\varphi\right\|\,\mathrm d\theta\,\mathrm d\varphi[/tex]
[tex]=\displaystyle100^2\int_{\varphi=0}^{\varphi=\pi/3}\int_{\theta=0}^{\theta=2\pi}\sin^2\theta\sin^3\varphi\,\mathrm d\theta\,\mathrm d\varphi[/tex]
[tex]=\dfrac{6250\pi}3[/tex]

Answer:

[tex]\iint_{s}^{} y^2 ds = \dfrac {6250\pi}{3}[/tex]

Step-by-step explanation:

Given :

[tex]x^2 +y^2+z^2=100[/tex]

[tex]x^2+y^2=25[/tex]

Solution:

Parameterize the region in spherical co-ordinates,

[tex]\rm r(\theta ,\phi)=\left\{\begin{matrix}x(\theta , \phi ) & = & 10\;cos\theta sin\phi \\ y(\theta , \phi ) & = & 10\;sin\theta sin\phi \\ z(\theta , \phi ) & = & 10\;cos\phi \end{matrix}\right.[/tex]

where, [tex]0\leq \theta \leq 2\pi[/tex]  and  [tex]o\leq \phi\leq \dfrac {\pi }{3}[/tex]  .Then,

[tex]\rm \left \|r_\theta\times r_\phi \right \| = \left \| \left \langle -100cos\theta sin^2\phi , -100sin\theta sin^2\phi,-100sin\phi cos\phi\right \rangle \right \|= 100sin\phi[/tex]

Surface integral,

[tex]\iint_{s}^{} y^2 ds = \iint_{s}^{} y(\theta ,\phi )^2 \left \| r_\theta\times r_\phi \right \|d\theta d\phi[/tex]

[tex]\iint_{s}^{} y^2 ds = 100^2\int_{\phi = 0}^{\phi = \frac{\pi}{3}}\int_{\theta=0}^{\theta =2\pi }sin^2\theta \; sin^3\phi \; d\theta \; d\phi[/tex]

[tex]\iint_{s}^{} y^2 ds = \dfrac {6250\pi}{3}[/tex]

For more information, refer the link given below

https://brainly.com/question/2289273?referrer=searchResults