Re: geometry question



On Mar 7, 1:29 pm, OwlHoot <ravensd...@xxxxxxxxxxxxxx> wrote:

[..]

Considering the various ways (p^2 + 1)(q^2 + 1)(r^2 + 1)
can be composed as a sum of two squares, this has a
general parametric solution (up to a scale factor,
which can be considered absorbed in the k_i) :

  k1.(x - a1)  =  p.q.r  -  p  +  q  +  r

  k1.(y - a2)  =  1      - q.r + r.p + p.q

  k2.(x - b1)  =  p.q.r  +  p  -  q  +  r

  k2.(y - b2)  =  1      + q.r - r.p + p.q

  k3.(x - c1)  =  p.q.r  +  p  +  q  -  r

  k3.(y - c2)  =  1      + q.r + r.p - p.q

Darn - The method needs fixing at this point

If there are three numeric values e_i with:

  k1.e1 + k2.e2 + k3.e3 = 0 [1]

e1 + e2 + e3 = 0 [2]

then the above system is consistent if and only if:

  f1.p    +  f2.q    +  f3.r    =  f4     [3]

  f1.q.r  +  f2.r.p  +  f3.p.q  =  f5     [4]

where the f_i are numeric:

One can always solve [1] and [2] to obtain e1:e2:e3
(As can be seen [1] eliminates x, y from the linear
combinations and [2] eliminates p.q.r and 1.)

However, f4 and f5 need not be zero, which makes
the formulae uglier.

No compellingly simple method to solve [3] and [4]
comes to mind, but I'll think about it.


Cheers

John Ramsden
.



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