Re: question about Solve

*To*: mathgroup at yoda.ncsa.uiuc.edu*Subject*: Re: question about Solve*From*: jacobson at cello.hpl.hp.com*Date*: Wed, 09 Jan 91 08:11:52 PST

Paul Schatz writes: > I want to solve some equations involving the matrix elements of > u--insuring of course that u be orthogonal. ... when I use Solve with > the two conditions orth1 and orth4, I get four solutions. The third of > these is correct. The others do not keep u orthogonal. Then I use > Solve again. This time I add the additional condition orth2. It seems > obvious to me that I should now get only the one correct solution. > But in fact, Solve reports no solutions. Solve frequently exhibits the problem of giving no solution. When you can get it to give you a list of solutions, one of which you know to be right (the case at hand) you can use this trick. Select[Solve[...], (criterion/.#)&] where "criterion" is an expresion that is true only for the correct answer. -- David Jacobson