From natural log to log base 10 The constraints of this question is related to a programming problem, but I must get the math right in order for it to be applied to code. The actual problem is I need a function that evaluates to log base 10 but all I have at my disposal is addition, subtraction, multiplication, division, a powering function, and a natual log function.  Is there a way to effectively evaluate log base 10 with the given operations?
On a side note, I seem to remember having to do some division with logs in order to change the base, but it's been forever ago (who knew those college math classes would come in handy!)

The change of base formula does it.
$$\log_{10}(x) = {\ln(x)\over \ln(10)}.$$
