Log Base A,B - Casio Fx9750-GII User Manual

Finding this function on the calculator takes several keystrokes. The following keystrokes

Log base a,b

will enable you to do other log bases other than 10.
The following figure is what you get after pushing the buttons.
You have done a log base 5 calculation. You are able to modify what is in the parentheses
and after comma. You are also able to add any combination of equations after the
parentheses.