[RESOLVED] Plot ellipse through apex and two other points

[boops boops]

The formula given here for the Steiner inellipse looks simple enough, but I am having trouble with understanding the notation:



The formula for g seems clear enough because I can treat it as two formulas:

g.X = (z1.X + z2.X + z3.X) / 3

and its counterpart for y.

That won't work for the main square root formula however (I tried it and it gave incorrect results). I considered interpreting g^2, z1z2 etc. as dot products of the vectors g, z1 etc. but the square root would then only produce a single number which can't be added or subtracted from g. As for the possibility that they are cross products, I don't know how to calculate them and I wouldn't know what meaning to give to the square root.

Can anyone enlighten me on this?

EDIT: the article mentions complex analysis, so presumably g and the z's are treated as complex numbers. I still can't resolve the formula -- what do I do with all the imaginary terms? But I'll do a bit of reading up.

EDIT 2: OK, I've sorted out the complex numbers with the help of WikiPedia. Now I have a working inellipse + circumellipse! My code needs a lot of tidying up but I'll post a demo soon.

BB