> Russell McMahon wrote: >> E = [(A^2-B^2)/(C^2+ 2.C.D + D^2)] x [(C+D)/(A-B)] x [ (C+D)/(A+B)] >> x >> F >> >> E will always equal F :-) > But that could just as well have been implemented by simply checking > A-D > according to some rules. ... Indeed. I think the object is to include a parameter (in my case 4 parameters) in the algorithm but for it/them to have no effect on the answer. I added the security part as a guess as to reason. RM -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist