1. The problem statement, all variables and given/known data f'(x) of log10 x 2. Relevant equations It's quite a nightmare to write on here if your not particularly fast with the code thing! 3. The attempt at a solution I eventually reached 1/x * log10e However, the answer should be 1/(x ln 10). Is there a stage from what I obtained that leads to the answer? If not, then there's something incorrect 'further up' the calculations and I'll go back and have a look... Just would appreciate some input as to whether or not I've arrived at a correct stage. Thanks.