How to calculate a PHI-ellipse defined by 3 points and its width/length ratio

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in the field of technical analysis for stock markets, the usage of so-called Phi-Ellipses is getting popular. One important property of this ellipses is its constant length/width ratio (e.g. 1.618).

Here is an (graphical) example:

http://img593.imageshack.us/img593/8708/qad.png

Given properties of the ellipse:

  1. The ellipse is defined by 3 points (point 0, 1 and 2).
  2. The ellipse has a given length/width ratio (e.g. 1.618).
  3. Point 0 is the outmost point on the major axis.

I would like to draw the phi-ellipse which fits to points 0, 1 and 2. To do so, I need to calculate the width or length of the ellipse (point 0 is already given).

Does anybody know how to calculate this parameter? (I would like to avoid an iterative algorithm because I think it can be calculated.)

Thank you in advance.