How would u differentiate the logarithm in which the base is the variable and the other number is a constant?
For example logx5 ?
If you didn't know the change of base rule...
$\displaystyle \displaystyle y = \log_{x}{(5)}$
$\displaystyle \displaystyle x^y = 5$
$\displaystyle \displaystyle \ln{\left(x^y\right)} = \ln{(5)}$
$\displaystyle \displaystyle y\ln{(x)} = \ln{(5)}$
$\displaystyle \displaystyle y = \frac{\ln{(5)}}{\ln{(x)}}$.