Logarithm

The base a logarithm of number b is the power to which number a must be raised in order to get number b

alogab=b
(log28=3  23=8)
a=10, log10x=lgx
a=e=2.718, logex=lnx

Important logarithm identities

logaa=1
loga1=0
logaan=n

Logarithmic identities

loga(xy)=logax+logay
loga(xy)=logaxlogay
logaxn=nlogax

Changing the base of a logarithm

logax=logbxlogba
logab·logba=1
alogbc=clogba
logax=loganxn
Keywords: logarithm