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Sunday, April 24, 2005

Mr K, I have a question....(^_^)

I'm just wondering about logarithm problems like 2^x = 3^(2x+5), (long answer 1.a on the pre-test) and the answer is x = (5ln3)/(ln2 - 2ln3). My question is, when should I use the "ln" instead of "log"? I mean, if I solved that problem using common log and got x = (5log3)/(log2- 2log3), am I wrong? I have no problem on dealing with exponents and logarithms (i hope so, for my sake), just the use of "ln" and "log" confuses me. Im thinking to ask this question tomorrow, but maybe you don't have time tomorrow to answer questions.


At 4/24/2005 4:16 p.m., Blogger Darren Kuropatwa said...

An excellent question!!

The answer is: it doesn't matter.

log (a) means log (base 10) of a
ln (a) means log (base e) of a

You could even use log (base 7) of a, but that base isn't programmed into our calculators so it would be a little harder to do (you would have to use the "change of base" formula). That's why we tend to use log (a) or ln (a). I generally like to use ln (a) ONLY because it's one less letter to write. ;-)

I hope this clears it up for everyone. If not, post about it again. ;-)


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