5.2b Change of Base of Logarithms

Change of Base of Logarithms

   logab=logcblogca         and      logab=1logba     

Example 1
:
Find the value of the following:
a. log25100
b. log30.45

Answer:
(a)  log25100=log10100log1025=log10102log1025=21.3979=1.431(b)  log30.45=log100.45log103=0.34680.4771=0.727



Example 2
Find the value of the following.
(a) log48
(b) log1255
(c) log8127
(d) log1664