The derivation of this law The derivation of this law is identical to the derivation of Logarithm Law 3 and is left as an exercise.
For example, show that log ( 10/1000 ) = log 10 − log 1000.
log (10)
log (1000)
log (10 / 1000) = log (1 / 100)
= log (10^(-2))
= -2