Hello my problem is with a bigger equation but the problem is bassicly this :
sage: var('x','y', domain=real)
sage: assume(x>0)
sage: assume(y>0)
sage: e = sqrt(1/y^2)y
sage: e.simplify_full()
1
sage: e = sqrt(x/y^2)y
sage: e.simplify_full()
y*sqrt(x/y^2)
Anyone explain me how to get just sqrt(x) and why it doesn't do directly? Thanks
I hope there is no way to coerce Sage into returning just x, because your expression is only equal to that for a very limited number of choices for x. Sage (Maxima, really) can be convinced to make branch choices to simplify the expression to sqrt(x), but not via assumptions, apparently. This does work:
sage: var('x,y')
(x, y)
sage: E=sqrt(x/y^2)*y
sage: E.canonicalize_radical()
sqrt(x)See the documentation of canonicalize_radical for details.
thank you, I edited
Yes, I mean just "x" part so sqrt(x)... sorry for not to be clear. Thanks. It works, but I wonder why canonicalize_radical isn't part of simplify_full?
This is because
sage: x = var('x', domain='real')
sage: assume(x<0)
sage: sqrt(x^2).canonicalize_radical()
xand I guess you don't want this (note the x<0 assumption).
Miguel, note that sqrt(x^2) != x for x<0.
I don't want this beacause is false. I want sqrt(x^2)=abs(x) or in case ofassume(x>0) or assume(x<0) : sqrt(x^2)=x or sqrt(x^2)=-x resp
I mean if I had the time and knowleage, I change it in the source code. Nevertheless, I'm thankful to all community of sagemath
A fix should be possible with pynac-0.4.x (pynac is part of Sage); pynac git master already does sqrt(x^2) --> x for x>0 as side effect of other changes.
Asked: 9 years ago
Seen: 844 times
Last updated: Sep 27 '15
Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
