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===Setup=== The surface of an ellipsoid with semi-major axes (a, b, c) is defined by the expression, <table border="0" cellpadding="5" align="center"> <tr> <td align="right"> <math>~1</math> </td> <td align="center"> <math>~=</math> </td> <td align="left"> <math>~\biggl( \frac{x}{a}\biggr)^2 + \biggl( \frac{y}{b}\biggr)^2 + \biggl( \frac{z}{c}\biggr)^2 \, .</math> </td> </tr> </table> This is identical to our expression for <math>~\lambda_1</math> if we make the associations, <table border="0" cellpadding="5" align="center"> <tr> <td align="right"> <math>~a = \lambda_1 \, ,</math> </td> <td align="center"> </td> <td align="center"> <math>~b = \frac{\lambda_1}{q} \ ,</math> </td> <td align="center"> </td> <td align="left"> <math>~c = \frac{\lambda_1}{p} \, .</math> </td> </tr> </table> Now, given that <math>~\lambda_3</math> does not functionally depend on <math>~z</math>, let's consider that the choice of <math>~z</math> is tightly associated with the specification of the second coordinate, <math>~\lambda_2</math>. Specifically, let's adopt the definition, <table border="0" cellpadding="5" align="center"> <tr> <td align="right"> <math>~\lambda_2^2</math> </td> <td align="center"> <math>~\equiv</math> </td> <td align="left"> <math>~1 - \biggl( \frac{z}{c}\biggr)^2 \, ,</math> </td> </tr> </table> in which case, we see that, <table border="0" cellpadding="5" align="center"> <tr> <td align="right"> <math>~z^2</math> </td> <td align="center"> <math>~=</math> </td> <td align="left"> <math>~c^2(1-\lambda_2^2) = \frac{\lambda_1^2(1-\lambda_2^2)}{p^2} \, ,</math> </td> </tr> </table> and, <table border="0" cellpadding="5" align="center"> <tr> <td align="right"> <math>~\biggl( \frac{x}{a}\biggr)^2 + \biggl( \frac{y}{b}\biggr)^2 </math> </td> <td align="center"> <math>~=</math> </td> <td align="left"> <math>~ \lambda_2^2 </math> </td> </tr> <tr> <td align="right"> <math>~\Rightarrow ~~~ x^2 + q^2 y^2 </math> </td> <td align="center"> <math>~=</math> </td> <td align="left"> <math>~ \lambda_1^2 \lambda_2^2 \, .</math> </td> </tr> </table> [Note that <font color="red">in the case of spherical coordinates</font> (q<sup>2</sup> = p<sup>2</sup> = 1), <math>~\lambda_1 \rightarrow r</math>, and this "second" coordinate, <math>~\lambda_2</math>, becomes <math>~\sin\theta</math>.] Combining this last expression with the <math>~x - y</math> relationship that is provided by the definition of <math>~\lambda_3</math>, gives, <table border="0" cellpadding="5" align="center"> <tr> <td align="right"> <math>~\lambda_1^2 \lambda_2^2</math> </td> <td align="center"> <math>~=</math> </td> <td align="left"> <math>~\frac{y^{2/q^2}}{\lambda_3^2} + q^2y^2 \, .</math> </td> </tr> </table> In general, the exponent of <math>~2q^{-2}</math> that appears in the first term on the right-hand side of this expression prevents us from being able to analytically prescribe the function, <math>~y(\lambda_1, \lambda_2, \lambda_3)</math>. But a solution is obtainable for selected values of <math>~q^2 > 1</math>.
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