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#1 2008-11-20 10:08:30
- BK
- Guest
Help with integral!
We are supposed to evaluate an appropriate integral to show that the surface area of the solid formed by rotating the circle x^2 + y^2 = r^2 about the x-axis is 4(pi)r^2. I can't understand it at all, can someone help!!!
#2 2008-11-20 11:49:32
- Daniel123
- Member
- Registered: 2007-05-23
- Posts: 663
Re: Help with integral!
The area of a surface formed when arc AB is rotated completely about the x-axis is:
It would be easier if you parametrised the equation of the circle and used:
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