00:01
In this problem we are asked to evaluate the double integral over the surface as curl of f, d s.
00:13
Here, f of x, y, z equals to x squared y cubed z i vector plus sign of x, y z j vector plus x, y z, j vector plus x, y z k vector, and the surface s is the region of the cone, y squared equals to x squared plus z squared that lies between y equals to 0 and y equals to 2 and the positive y axis.
00:54
So here we make use of the stokes theorem.
00:57
The stokes theorem states that the double integral over s curl of fds equals equals.
01:03
Equals to the integral over c fdr.
01:08
So here we need to parameterize c.
01:13
We can rewrite x as 2 times cos of t, y as 2 times sine of t and sorry z as 2 times sine of t and y as 2.
01:29
So we obtain r of t to be equal to 2 2 cos of t to 2 sine of t.
01:40
So now let us differentiate this.
01:43
We get dr to be equal to negative 2 sine of t 0 and positive 2 cost of t.
01:51
Now let us substitute this value of r in f.
01:56
So we get f of r of t to be equal to 4 times cos squared t times 8.
02:07
Times 2 times sine of t i vector plus sign of 8 times cos of t sine of t j vector plus 8 times cos of t times sine of t k vector so simplifying this we have f of t to be equal to 64 cost square t times sine of t, sign of 8 times cos of t sign of t, and 8 times cost of t, sign of t...