On Aug 20, 3:43 pm, Mike Hansen <[email protected]> wrote: > On Fri, Aug 20, 2010 at 12:31 PM, michel paul <[email protected]> wrote: > > sage: _ / -3 > > x |--> x > (8/3) > > > The '>' should be '<'. > > A conscious decision was made for this not to be the case since one > has to check whether or not the operand being applied is less than or > greater than zero. In your specific case, it is easy. However, there > are many times where it is not so clear cut. Consider the case where > you divided by another variable 'a'. Then, should you change the > direction of the inequality or not? Similarly, you could multiply by > something that is zero but not Sage cannot prove that it is zero.
Good answer. Of course, then the question is whether we should allow one to multiply/divide a relation at all since weird things might happen. I think that Michel has a point that Sage is allowing mathematically wrong output. Are there places elsewhere where 'doing the same thing to both sides' is used? - kcrisman Maybe this belongs on sage-support... -- You received this message because you are subscribed to the Google Groups "sage-edu" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sage-edu?hl=en.
