12

It is stated at the Wolfram Documentation Center (FullSimplify/Possible Issues) that:

enter image description here

Why and when this could happen? How to avoid it? Any patterns?

Edit:

As pointed out in the comments, this question is a duplicate.

Community
  • 1
Giovanni F.
  • 1,911
  • 13
  • 20
  • The first examle mighe be FullSimplify[(1 - b^2)/c^2, c^2 + b^2 == 1]. – Artes Dec 02 '14 at 13:54
  • 1
    @Artes yes, it seems that the alphabetic order is the problem. The symbol inside the parenthesis has to come first considering the alphabet order. It's obvious with these examples : FullSimplify[(1 - abx^2)/aby^2, abx^2 + aby^2 == 1] and FullSimplify[(1 - aby^2)/abx^2, abx^2 + aby^2 == 1]. The first example gives 1 because abx is "before" aby (if you sort them alphabetically) ... – SquareOne Dec 02 '14 at 14:10
  • Why doesn't Wolfram relabel the symbols, simplify, and restore the original names...? – tclamb Dec 02 '14 at 15:59
  • 3
    I have the impression that this happens because trying out all possible replacements would involve going through large numbers of permutations which would generally lead to a combinatoric explosion. So, some choices have to be made, and not all possible replacements are actually tried. – Sjoerd C. de Vries Dec 02 '14 at 16:42
  • Maybe an option should be available for us. – Giovanni F. Dec 02 '14 at 16:43
  • Closely related: Why does Simplify ignore an assumption? (possible duplicate?). There's a solution in Mr.Wizards answer. – jkuczm Dec 06 '14 at 10:52
  • That's right. It is a duplicate. – Giovanni F. Dec 06 '14 at 14:26

0 Answers0