On Thu, Dec 4, 2014 at 10:25 AM, Paul Royik <distantjob...@gmail.com> wrote:
> I know this way, but is there any way to change this after symbol creation?
The right way in my opinion is to just create a symbol with no
assumptions and then use refine(). As I wrote below, it doesn't yet
work for this case, but it will in the future. If you have time, we
would appreciate any help with this.
Ondrej
>
> On Thursday, December 4, 2014 6:29:27 PM UTC+2, Ondřej Čertík wrote:
>>
>> On Thu, Dec 4, 2014 at 7:38 AM, Paul Royik <distan...@gmail.com> wrote:
>> > Suppose that I have an expression
>> >
>> > e = x**2+sqrt(a**2*b**2)
>> > What is the best way to assign to expression assumption that all
>> > variables
>> > are Positive, so that equivalent of e is x**2+ab?
>>
>> It should be done like this:
>>
>> In [11]: refine(e, Q.positive(a) & Q.positive(b))
>> Out[11]:
>> _______
>> 2 ╱ 2 2
>> x + ╲╱ a ⋅b
>>
>>
>> But unfortunately that doesn't work. So the only other way is the old
>> way like this:
>>
>> In [12]: a = Symbol("a", positive=True)
>>
>> In [13]: b = Symbol("b", positive=True)
>>
>> In [14]: x**2+sqrt(a**2*b**2)
>> Out[14]:
>> 2
>> a⋅b + x
>>
>>
>> Ondrej
>
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