also (a**2)**0.5 and (a)**1 are not the same things ..
On Mon, Feb 20, 2012 at 2:35 PM, Chris Smith <[email protected]> wrote:
> Since such a transformation is not generally valid, it is disallowed (e.g.
> if a = -1 then your expression would give 1 while the "simplified" version
> would give -1). The transformation *is* valid if 'a' is positive, so you
> can either create a with a positive assumption
>
> >>> a = Symbol('a', positive=True)
> >>> (a**2)**.5
> a
>
> or let posify handle the conversion:
>
> >>> eq
> (a**2)**0.5
> >>> posify(eq)
> (_a**1.0, {_a: a})
> >>> p, r = posify(eq); p.subs(r)
> a
>
> Chris
>
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