Posted by Weasel on 1999-04-15
Frank Hale wrote:
>
> I hate to sound ignorant but what is a logarithm anyway? What is it used
> for?
You know the power function? i.e. 10 to the power of 3 which simply is
10 x 10 x 10, or 2 to the power of 5 which is 2 x 2 x 2 x 2 x 2 = 32.
Ok, what do you do if you know, that x to the power of 2 = 9? right, do
use the square root function; e.g. sqrt(9) = 3 or sqrt(16)=4. if you
know x to the power of 6 is 64, you simply use the 6 th root, since the
6 th root of 64 is 2.
so, you know what to do when you have
* a^b = c and you know a,b. simply raise a to the power of b, i.e. a
times a times a times ... times a (with a occuring excatly b times)
* a^b = c and you know b,c. use the b-th root.
but what if you have a^b = c and you know a and c: well that's what the
log is for:
log of 100 to the base of 10 is 2 since 10^2 is 100
log of 156 to the base of 2 is 8 since 2^8 is 256
usually if you simply write log without giving any base, then 10 is the
base.
if you use ln, then the base is e, which is about 2.7.... e is a number
that appears very often in natural sciences, just like pi
(=3.1415926535....)
HTH and please excuse my bad math-english.
--
Weasel mailto:palfrader@xxxxxxx.xxx
Peter http://www.cosy.sbg.ac.at/~ppalfrad/
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