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## [Axiom-math] About rewrited expressions for power, log, exp and so.

**From**: |
Francois Maltey |

**Subject**: |
[Axiom-math] About rewrited expressions for power, log, exp and so. |

**Date**: |
30 Nov 2006 15:52:18 +0100 |

**User-agent**: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.4 |

Hello,
I try to understand how axiom is sure in Expression domain.
and what suppositions axiom does.
It seems that axiom makes a lot of fuzzy simplifications.
Of corse it's possible to delete such rules in elemntry.spad.
But then how can I test if standard exemples of axiom continue to be right
with a new elemntry.spad ?
sqrt (u^2) ---> sqrt (u^2) I agree sqrt ((-1)^2) = 1
but (u^a)^(1/a) ---> u not coherent with a=2
(u^a)^2 ---> u^(2a) is right
but (u^a)^b ---> u^(ab) I prefer (u^a)^b
and (u^2)^a ---> u^(2a)
u^a*u^b ---> u^a u^b is right but u^(a+b) is also possible.
The question is the same for asin (sin x), log (exp x), etc.
For sin it's line 486 in elemntry.spad
What rules might apply axiom for expressions ?
Is there a reason that theses rules aren't usual mathematic rules ?
What is the axiom policy ? What is your advice ?
Have a nice day.
Francois

**[Axiom-math] About rewrited expressions for power, log, exp and so.**,
*Francois Maltey* **<=**