The natural logarithm (symbol ln) is widely used in the sciences.
While the notation log10(x) and loge(x) may be used, log10(x) is often written log(x) in Science and
loge(x) is normally written as ln(x) in both Science and Mathematics. So, if you see the log symbol
without a base, it means log10.
Logarithms can be changed from one base to another, by using the change of base formula:
log y x
log a x = --------
log y a
where y is any base you find convenient.
Normally a and y are known, therefore logy a is normally a
known, if irrational, number.
for example :
log 10 13
log 4 13 = --------
log 10 4
log 10 16
log 4 16 = --------
log 10 4
