Question 134545:  Dear Tutor,
 
I have searched google and relevant pages on logarithms, and whilst I think I now understand them in principle and am able to solve simple questions I am totally unable to use my calculator to solve e.g.
 
log (to base 2) 512 = 9.  OR log (to base 2) 16 = 4
 
I can't find any webpage that will tell me what to type into my calculator (the calculator's instruction manual is equally useless).
 
I have a common scientific calculator (CASIO fx-85 MS, similar to the fx-300MS). Please coud you tell me exactly what buttons I need to press in order to solve this type of problem.
 
Thank very much,
 
 
Edward S 
 Answer by vleith(2983)      (Show Source): 
You can  put this solution on YOUR website! The equations you posted are not asking to solve anything. They are just "true"
 
Given: log (to base 2) 512 = 9
 
Let's suppose the question was  
log (to base 2) 512 = x    find x 
There are 2 ways to do this
 
1) Use the values on both sides of the equation as exponents. Since the log2 is used, make the base 2.
 
2^(log (to base 2) 512) = 2^x 
A base raised to the log of that base is just the exponent. 
Thus: 
512 = 2^x 
What power of 2 is equal to 512? 2^9
 
The second way to solve these, and the one you are most likely to want to understand is
 
Log 2 (512) = Log10(512)/Log10(2) 
And Log10 is just your plain old Log function on your calculator.
 
So, Log(512) =  2.7109 
Log(2)= 0.301 
Log(512)/Log(2) = 9 !!
 
use the same method for your second equation.
 
Does that help? 
 
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