ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Wed, 03 Feb 2016 00:46:32 +0100How do I back substitute in output.https://ask.sagemath.org/question/32422/how-do-i-back-substitute-in-output/ I define three points (xia,yia,zia,xib...), the vectors xab,yab,zab,xcb.. , the distances rab2 and rcb2, the dot product, the angle a-b-c and then the energy of bending the angle - e. I take the derivative of e with respect to xia and I get a long output in terms of xia-xib, xic-xib and so on. I want to condense the output by using all the previous defines. I normally would do this by hand doing string replacements in emacs. Tedious and error prone. Is there a command or script that will do the back substitution. Simplify dies with out of memory errors and is not really what I am trying to do. I had the same problem in Mathmatica and never found a good solution.KevinGilbertWed, 03 Feb 2016 00:46:32 +0100https://ask.sagemath.org/question/32422/