On Mon, Aug 3, 2009 at 4:42 PM, Johan Ekh<[email protected]> wrote:
> Hi all,
> I am new to SymPy. I'm trying to simplify an expression that contains
> "sqrt".
> SymPy refuses to do what I want. I want to simplify the expression f2
> below into
> x**2/y but I can't get it, see my session below. I use version 0.64
> on OpenSuSE 11.1 64bit.
>
> Best regards,
> Johan
>
>
> In [91]: x = Symbol('x')
> In [93]: y = Symbol('y')
> In [94]: f = x**4/y**2
> In [95]: f
> Out[95]: x**4/y**2
> In [96]: f2 = sqrt(f)
> In [97]: f2
> Out[97]: (x**4)**(1/2)*(y**(-2))**(1/2)
> In [98]: simplify(f2)
> Out[98]: (x**4)**(1/2)*(y**(-2))**(1/2)
SymPy assumes that your symbols are complex, so it can't do anything
about it. If you tell it that they are real (or even positive), it can
do more simplifications:
In [5]: x = Symbol('x', real=True)
In [6]: y = Symbol('y', real=True)
In [7]: f = x**4/y**2
In [8]: f
Out[8]:
4
x
──
2
y
In [9]: f2 = sqrt(f)
In [10]: f2
Out[10]:
2
x
───
│y│
Ondrej
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