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