The subs for s = sqrt(x**2 + y**2 + z**2) should work. To make the other one work, try subs(x**2, s**2 - y**2), followed by a call to factor().
Aaron Meurer On Fri, Apr 4, 2014 at 11:14 AM, Dave M <[email protected]> wrote: > Hi > I've tried subs() for this but it's not working for me. I have the > following expression: > > j*(3*x**4 + 6*x**2*y**2 - 24*x**2*z**2 + 3*y**4 - 24*y**2*z**2 + > 8*z**4)/(2*(x**2 + y**2 + z**2)**(9/2)) > > I want to simplify it by making the substitutions r = sympy.sqrt(x*x + y*y > + z*z) and s = sympy.sqrt(x*x + y*y) so that it becomes something like > > j/r**9*(4*z**2*(z**2 - 3*s**2) + 3/2*s**4) > > can this be done with sympy, and if so how? > Thanks > > > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/a1c4dbb4-0263-495b-9a54-18fd33c4d431%40googlegroups.com<https://groups.google.com/d/msgid/sympy/a1c4dbb4-0263-495b-9a54-18fd33c4d431%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6KjfDLdzXgpviL_SVma5bR2eoUc2YMCr7EA10Q9gJBTVw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
