# help needed with logs

• March 24th 2009, 07:21 AM
lauratree
help needed with logs
I have the example log 2 8 = 3
but i cant figure out what keys to press on the calculator to work this out myself! help please!
• March 24th 2009, 07:25 AM
Pinkk
The point of these problems is to help you understand what the $log$ function actually entails. $log_{a}b=x \Rightarrow a^{x}=b$ Applying that to the one you have:

$log_{2}8=x \Rightarrow 2^{x}=8$ The answer should be somewhat obvious.
• March 24th 2009, 07:26 AM
stapel
Quote:

Originally Posted by lauratree
I have the example log 2 8 = 3
but i cant figure out what keys to press on the calculator to work this out myself! help please!

If you must use a calculator (rather than the simpler definition of logs), then you'll need to use the change-of-base formula to convert the base-two log to either a base-10 or base-e log.

. . . . . $\log_b(x)\, =\, \frac{\log_a(x)}{\log_a(b)}$

...where "b" is the original base and "a" is the base you're changing to.

(The answer will be the same, regardless of the base you choose. But you have to use a base that your calculator can understand.)

(Wink)