A colleague has pointed me to the book "Divine Proportions: Rational Trigonometry to Universal Geometry" by N J Wildberger (Assoc Prof UNSW Sydney) See http://wildegg.com/products.htm I am not into geometry but some people on the list surely are. Therefore this posting. -- p=2^q-1 prime <== q>2, cosh(2^(q-2)*log(2+sqrt(3)))%p=0 Life is hard and then you die.