Can someone help please

Use Stokes' Theorem to evaluate C F · dr F(x, y, z) = xyi + yzj + zxk, C is the boundary of the part of the paraboloid z = 1 − x

Serggg [28]

I assume $C$ has counterclockwise orientation when viewed from above.

By Stokes' theorem,

$\displaystyle\int_C\vec F\cdot\mathrm d\vec r=\iint_S(\nabla\times\vec F)\cdot\mathrm d\vec S$

so we first compute the curl:

$\vec F(x,y,z)=xy\,\vec\imath+yz\,\vec\jmath+xz\,\vec k$

$\implies\nabla\times\vec F(x,y,z)=-y\,\vec\imath-z\,\vec\jmath-x\,\vec k$

Then parameterize $S$ by

$\vec r(u,v)=\cos u\sin v\,\vec\imath+\sin u\sin v\,\vec\jmath+\cos^2v\,\vec k$

where the $z$ -component is obtained from

$1-(\cos u\sin v)^2-(\sin u\sin v)^2=1-\sin^2v=\cos^2v$

with $0\le u\le\dfrac\pi2$ and $0\le v\le\dfrac\pi2$ .

Take the normal vector to $S$ to be

$\vec r_v\times\vec r_u=2\cos u\cos v\sin^2v\,\vec\imath+\sin u\sin v\sin(2v)\,\vec\jmath+\cos v\sin v\,\vec k$

Then the line integral is equal in value to the surface integral,

$\displaystyle\iint_S(\nabla\times\vec F)\cdot\mathrm d\vec S$

$=\displaystyle\int_0^{\pi/2}\int_0^{\pi/2}(-\sin u\sin v\,\vec\imath-\cos^2v\,\vec\jmath-\cos u\sin v\,\vec k)\cdot(\vec r_v\times\vec r_u)\,\mathrm du\,\mathrm dv$

$=\displaystyle-\int_0^{\pi/2}\int_0^{\pi/2}\cos v\sin^2v(\cos u+2\cos^2v\sin u+\sin(2u)\sin v)\,\mathrm du\,\mathrm dv=\boxed{-\frac{17}{20}}$

6 0

3 years ago

The age of a boy is twice that of his sister. five years ago the boy was 3 times the age of his sister. How old is the boy

joja [24]

Answer:

<h2>20 years old.</h2>

Solution,

Let the age of sister be X

Let the age of boy be 2x

Now,

Five years ago,

 $3(x - 5) = 2x - 5 \\ or \: 3x - 15 = 2x - 5 \\ or \: 3x - 2x = - 5 + 15 \\ x = 10$ 

Again,

Replacing value,

 $age \: of \: boy = 2x \\ \: \: \: \: \: \: \: \: \: \: \: \: \: = 2 \times 10 \\ \: \: \: \: \: \: \: \: \: \: \: = 20$ 

hope this helps..

Good luck on your assignment..

7 0

3 years ago

Determine the vertex of the parabola:

Elza [17]

Answer:

Be more clear please

Step-by-step explanation:

7 0

3 years ago

Debra Goforth's savings account shows a balance of $904.31 on March

yanalaym [24]

Answer:

Debra Goforth's savings account shows a balance of $904.51 on March 1. The same day, she ... of $904.51 on March 1. The same day, she made a deposit of $375.00 to the account. She also made deposits of $500.00 on April 1 and May 1. The bank pays interest at a rate of 5.5 percent compounded daily.

Step-by-step explanation:

Hope this helps!

4 0

3 years ago

Which functions can have a vertex?

vovikov84 [41]

Answer:

quadratic functions have a vertex

6 0

2 years ago