ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Fri, 17 Jan 2014 16:38:00 +0100simplify_full - is the mistake in the documentation or the source code?https://ask.sagemath.org/question/10939/simplify_full-is-the-mistake-in-the-documentation-or-the-source-code/Looking at the simplify_full documentation in Sage 6.0, it says that it
> Applies simplify_factorial,
> simplify_trig, simplify_rational,
> simplify_radical, simplify_log, and
> again simplify_rational to self (in
> that order).
However the source code is
def simplify_full(self):
x = self
x = x.simplify_factorial()
x = x.simplify_trig()
x = x.simplify_rational()
x = x.simplify_log('one')
x = x.simplify_rational()
return x
So where is the mistake? Should simplify_radical be added to the source code or removed from the documentation?brkirchFri, 17 Jan 2014 16:38:00 +0100https://ask.sagemath.org/question/10939/simplification errors in simple expressionshttps://ask.sagemath.org/question/8324/simplification-errors-in-simple-expressions/I'm currently testing the possibilities of SAGE as a teaching aid in a high school math course (in Belgium). I stumbled upon this:
- When evaluating x/sqrt(x^2), SAGE answers $\frac{x}{|x|}$, as it should. Appending a ***.simpify()***-instruction to the input does not change anything.
- However, `((1-x^2)/sqrt(1-2*x^2+x^4)).simplify_full()` evaluates to $-1$, in stead of $\frac{1-x^2}{|1-x^2|}$.
As an aside, it's definitely baffling that a behemoth program like SAGE is outdone in this respect by a one-floppy-disk, antique program called DERIVE.
As another aside, I still have to find a meaningful use for the instruction ***simplify()***. Can someone provide me an expression that is actually simplified by simplify()?
***Note added:***
I'm not sure I'm satisfied with mr. Fateman's answer (and I definitely disagree that defining sqrt(x^2)=|x| - for real x - entails +1=-1). But what I really want to know is this: is there a SAGE object that represents (reliably) the positive square root of a positive real number x? (Surely a quantity that is not without interest.) And how do I define it in SAGE?Dirk DanckaertThu, 22 Sep 2011 17:53:33 +0200https://ask.sagemath.org/question/8324/