Hi, I got the following in Maxima: (%i1) declare(a,real,b,real); (%o1) done (%i2) c:a+b; (%o2) b + a (%i3) is(c^2>0); (%o3) unknown I know that "is" in Maxima is not very strong, but this is really trivial. Is there something I'm doing wrong? Thanks, Best Regards Sergio