On 7/2/07, David Harvey <[EMAIL PROTECTED]> wrote:
>
> Because I is the square root of -1.
Yep. If you want I to be a symbolic variable do
sage: I = var('I')
sage: a = E == I * R
sage: solve(a, R)
[R == (E/I)]
In general, it is always a good idea to use the var command to
explicitly construct any symbolic variables you are going to use.
It's a flexible and easy-to-use command. Not only does it
allow many variables in input (separated by spaces), but it
returns them as a tuple and also defines all the variables
as a side effect (at least when used interactively from the prompt):
sage: var('a b I XYZ theta')
(a, b, I, XYZ, theta)
sage: theta
theta
-- William
>
> sage: type(I)
> <class 'sage.functions.constants.I_class'>
>
> sage: type(J)
> <class 'sage.calculus.calculus.SymbolicVariable'>
>
> sage: type(R)
> <class 'sage.calculus.calculus.SymbolicVariable'>
>
> Yeah this is pretty confusing if it's not what you expected.
>
> david
>
> On Jul 3, 2007, at 7:18 AM, Ted Kosan wrote:
>
> >
> > Does anyone have any thoughts on why solve() returns [R == -1*I*E] in
> > the following SAGE session?
> >
> > Thanks in advance :-)
> >
> > Ted
> >
> > ----------------------------------------------------------------------
> > | SAGE Version 2.6, Release Date: 2007-06-02 |
> > | Type notebook() for the GUI, and license() for information. |
> > ----------------------------------------------------------------------
> >
> > sage: a = E == I * R
> >
> > sage: a
> > E == I*R
> >
> > sage: solve(a,I)
> > [I == (E/R)]
> >
> > sage: solve(a,R)
> > [R == -1*I*E]
>
>
> >
>
--
William Stein
Associate Professor of Mathematics
University of Washington
http://www.williamstein.org
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