Eliminate Parameters to Find Ellipsoid Cartesian Equation

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Homework Statement


Eliminate the parameters u and v to obtain a Cartesian equation, thus showing that the given vector equation represents a portion of the surface named. Also, compute the fundamental vector product dr/du x dr/dv in terms of u and v.

Homework Equations

Ellipsoid
r(u,v) = asinucosvi + bsinusinvj + ccosuk

The Attempt at a Solution

I can find the cross product easy enough(abcsinu((sinucosv/a)i+(sinusinv/b)j+(cosu/c)k), but how should I go about getting rid of the parameters?
 
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Let x = asinu*cosv, y = bsinu*sinv, and z = ccosu.

You can combine x and y by using the identity sin^2(t) + cos^2(t) = 1. That's where I would start.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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