How to put "log" into the calculator?

Question

I know that "log" = log sub 10 for default of caculators
how would I put (log sub 2)5 on the calculator? sub=small number on bottom

Thanks
Narumi

Answer 1

You'd probably have to use the change of base formula, most calculators only do logs in base 10 and e.
So if you want, for example, log base 2 of 5 you'd have to enter (log 5)/(log 2) or (ln 5)/(ln 2)
for more explanation on this see
http://www.sosmath.com/algebra/logs/log4/log43/log43.html
You could probably program this into your calculator, or, if you have an advanced model calculator you may have it in the menus. Look in your calculator instruction book for "logarithm change of base formula"

Answer 2

You have to use the Change of Base formula, which goes as follows:

log[base c](a) = log[base b](a) / log[base b](c)

This means you can effectively CHOOSE your base b, so long as you express it as a quotient with the log[base b] of the former base.

If you wanted to calculate log[base 2](5), you would choose base 10 (which is what log is, on your calculator), or base e(which is ln on your calculator).

log[base 2](5) = log(5) / log(2)

OR

log[base 2](5) = ln(5) / ln(2)

Both should yield the same result.

Answer 3

Your calculator probable solves from left to marvelous, like 40+40=eighty, 80x0=0, 0+a million=a million. in case you want your calculator to get the final answer, positioned 40x0 in first (by way of fact multiplication is going first by utilising order of operations), then +40+a million.