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# Volume of revolution help? watch

1. The question is: The region R is bounded by the curve y = 4 +3sec2x, the x-axis and the lines x=-pi/6 and x=pi/6. Find the volume of the solid formed by rotating R through 2pi radians about the x-axis.

I get to the stage where I have pi (9/2tan2x + 12ln(sec2x + tan2x) + 16x) with the limits but I cant seem to get the answer in the back when I substitute which is 200.907
2. (Original post by wannabe_lawyer)
The region R is bounded by the curve y = 4 +3sec2x, the x-axis and the lines x=-\frac{\pi}{6} and x=\frac{\pi}{6}. Find the volume of the solid formed by rotating R through 2\pi radians about the x-axis.
Are you familiar with this formula:
3. (Original post by wannabe_lawyer)
The region R is bounded by the curve y = 4 +3sec2x, the x-axis and the lines x=-\frac{\pi}{6} and x=\frac{\pi}{6}. Find the volume of the solid formed by rotating R through 2\pi radians about the x-axis.
Use the pi y^2 formula
5. (Original post by Naruke)
Are you familiar with this formula:
(Original post by beastmode1)
Use the pi y^2 formula
I used the formula (That's how I got to the stage). I'm wondering if I've integrated wrong.
6. (Original post by wannabe_lawyer)
The question is: The region R is bounded by the curve y = 4 +3sec2x, the x-axis and the lines x=-pi/6 and x=pi/6. Find the volume of the solid formed by rotating R through 2pi radians about the x-axis.

I get to the stage where I have pi (9/2tan2x + 12ln(sec2x + tan2x) + 16x) with the limits but I cant seem to get the answer in the back when I substitute which is 200.907
You are probably expanding it wrong should get 64
7. (Original post by beastmode1)
You are probably expanding it wrong should get 29
8. (Original post by wannabe_lawyer)
I used the formula (That's how I got to the stage). I'm wondering if I've integrated wrong.
There are many ways to go about solving an integral, so just giving us the stage you got to doesn't help us much. We need line by line steps, if possible...
9. (Original post by wannabe_lawyer)
No I got 64 lol I made a mistake

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