00:01
So this question we have a solid bounded by some curves.
00:08
So here's x, y.
00:10
We have the line y equals zero.
00:13
So this is the x -axis.
00:15
We have the line y equals cos of 6x.
00:19
So that's going to look like this.
00:26
So if this is cos of 6x, then this is going to go to zero when 6x is 5x is when 6x is 5.
00:35
Is pi divided by 12.
00:38
And funnily enough, the line x equals pi divided by 12 is also a boundary.
00:44
And so is the line x equals zero.
00:47
So that is the y -axis.
00:51
And we want to rotate this around the axis.
00:54
So this is our region in here.
00:55
This is our region.
00:59
And we will rotate this around the line.
01:01
So let's just actually get rid of this.
01:07
So this is 1.
01:09
This line is cos 6x.
01:12
And we want to rotate this around the axis x equals 8.
01:20
So what is the volume of revolution? well, the volume is the double integral over the area of the region r of 2 pi times the distance from the line x equals 8.
01:33
So that's going to be 8 minus x, dx, dy...