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Stupid Logs
*To*: mathgroup at yoda.physics.unc.edu (Mathematica User's Group)
*Subject*: Stupid Logs
*From*: Keith Clay <clay at galileo.phys.washington.edu>
*Date*: Thu, 25 Jun 92 15:06:04 MDT
Question: Why is Mathematica's Log function so stupid when there is so much
intelligence in the trig functions?
A few of us have noticed tha Mathematica is at a loss for simplifying even the
simplest functions involving logarithms.
Two examples follow.
1) Try asking Mathematica to simplify
Log[(1+2x+x^2)/(1-x^2) - x/(1-x)] + Log[1-x]
It will simplify the first Log ARGUMENT to be 1/(1-x), but it doesn't seem
to know that Log[1/a_]:=-Log[a].
You can Unprotect Log and tell it this, but why do we have to?
2) Mathematica is completely at a loss as to how to simplify the following.
>
> 2
> 19683 a (96 Pi )/l 2
> > 2 l Log[----------------])) / (67108864 E Pi ) +
> 2
> (48 Pi )/l
> 1024 E
>
` You can probalby simplify it in your head, but unprotecting and redefining
all of the rules that are needed takes forever.
DOES ANYBODY KNOW A SIMPLE WAY TO DO THIS???
Keith
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