With the change of base formula, logb(A)=logc(A)logc(b) for any bases b, c>0, we can finally find a decimal approximation to our question from the beginning of the...With the change of base formula, logb(A)=logc(A)logc(b) for any bases b, c>0, we can finally find a decimal approximation to our question from the beginning of the section. The logarithm (base b) function, written log b (x), is the inverse of the exponential function (base b), b x . Properties of Logs: Change of Base: logb(A)=logc(A)logc(b) for any base b,c>0