The last topic that we have to discuss in this section is the change of base formula.

Most of the calculators these days are able of evaluating common logarithms & natural logarithms. Though, that is regarding it, so what do we do if we have to evaluate another logarithm which can't be done simply

In order to do this we have the change of base formula.  Following is the change of base formula.

                       log _a x = log_b  x / log_b  a

Where we can select b to be anything we desire it to be. To use this to help us evaluate logarithms it is usually the common or natural logarithm.  Following is the change of base formula by using both the common logarithm & the natural logarithm.

log_a x = log x / log a                         log_a x = ln x / ln a