something like:
In [1]: a, b, c = symbols('abc')
In [2]: f = a + b + c + a**2 + b**2 + c**2
In [3]: f.subs(a**2 + b**2 + c**2, 1)
Out[3]: 1 + a + b + c
In [4]: xsq = a**2 + b**2 + c**2
In [5]: xsq.args[0]
Out[5]:
2
a
In [6]: new_xsq = xsq - a**2 - 1
In [7]: new_xsq
Out[7]:
2 2
-1 + b + c
In [8]: f.subs(xsq, new_xsq)
Out[8]:
2 2
-1 + a + b + c + b + c
If not give a snippet of what you want, I get a little confused with
all the word place holders.
-- Andy
On Thu, Dec 4, 2008 at 1:30 PM, Alan Bromborsky <[EMAIL PROTECTED]> wrote:
>
> Say I have a expression f containing symbols a, b, c, a**2, b**2, and
> c**2 and I wish to automate imposing the constraint a**2+b**2+c**2 =
> 1. But a,b, and c and their squares are hidden (were generated by other
> manipulations) so all I have are f and xsq (xsq = a**2+b**2+c**2). How
> do I extract the first square from xsq so that I can:
>
> new_xsq = xsq-a**2-1 and then substitute new_xsq into f eliminating a**2
> from f (I actually don't care whether I eliminate a**2 or b**2 or c**2).
>
> >
>
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