ASKSAGE: Sage Q&A Forum - Latest question feedhttp://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Sat, 11 Feb 2012 04:56:41 -0600Symbolic solvehttp://ask.sagemath.org/question/8707/symbolic-solve/Following the [change of variable thread](http://ask.sagemath.org/question/1113/change-of-variable-in-an-integration), I wanted to streamline the whole process.
Namely, using the same example in the above thread, I'd like to say
integral_def_change(x*cos(x^2+1), (x, 0, 2*pi), u==x^2+1, u)
The difference is, I wanted also Sage to automatically solve for x instead of providing x= sqrt(u-1), say. But when I tried
solve(u==x^2+1, x)[0].rhs()
the output was `r1` ???
1- What exactly is r1 ??
A way out (see this [thread](http://ask.sagemath.org/question/1105/solve-and-calculate)) seems to make of the solution a function of `u`
f(u)=solve(u==x^2+1, x)[0].rhs()
Now f is
u |--> -sqrt(u - 1)
2- What can I do to get +sqrt(u - 1) instead? Is this related to the [positive function question there](http://ask.sagemath.org/question/989/is-it-possible-to-define-or-assume-a-general)?Green diodSat, 11 Feb 2012 04:56:41 -0600http://ask.sagemath.org/question/8707/