Original poster: "Godfrey Loudner" <ggreen-at-gwtc-dot-net>
Hello Antonio
I don't know why I'm posting this, but that sign function in
the expression for Cos[alpha] is unnesessary. Better to write
Cos[alpha] as the absolutevalue{d-(D-d)Cos[theta]} divided
by D-d-dCos[theta]. Of course you would have noticed this.
A guess I had a little too much Christmas beer.
Godfrey Loudner