Okay. I think you mean that if you rotate a semi-circle around its diameter you create a sphere, and the method of disks will give the volume of that sphere. If you rotate half an ellipse around one of its axes you produce an ellipsoid and the method of disks will give the volume of this ellipsoid. However, these are special cases. These produce ellipsoids one of whose cross-sections is a circle. The volume of these ellipsoids will be (4/3)pi a b^2 or (4/3) pi a^2 b. The general ellipsoid is not a soid of revolution.
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-----Original Message----- From: Kevin Regardie [mailto:email@example.com] Sent: Friday, May 25, 2012 9:50 AM To: AP Calculus Subject: Re:[ap-calculus] ellipsoid