calculator help with log base 10??

[James Wraith]

I'm not sure of the notation used in this group for log base 10??? Can
anyone help me I want to know how to use my calculator to perform
calculations like the following:

log2 (8) = 3
or
log 10 (100) = 2

I'm using a Casio scientific calculator and cannot figure out the
buttton sequence.

Thanks
James

[Elizabeth Stapel]

James Wraith <capti...@usa.net> wrote:

>log2 (8) = 3
For this, use the change-of-base formula.

>log 10 (100) = 2

Any calculator that has a "log" button can
do this, because "log" means "log base 10",
also known as "common log".

Eliz. Stapel
(remove *nospam* to reply privately)
Purplemath - Your Algebra Resource!
http://www.purplemath.com/

[James Wraith]

What is the change-of-base formula?
James

[James Wraith]

never mind that was the next chapter thnks anyway ; )

[Stan Brown]

[This followup was also e-mailed to the cited author for speed.
Please follow up in the newsgroup.]

Said capti...@usa.net (James Wraith) in alt.algebra.help:

>I'm not sure of the notation used in this group for log base 10??? Can
>anyone help me I want to know how to use my calculator to perform
>calculations like the following:
>
>log2 (8) = 3
>or

>log 10 (100) = 2

Basically, all the logs to any given base are proportional to the
logs to a different base. This is expressed in the change-base
formula, which you will find at
http://www.mindspring.com/~brahms/log-base.htm
among other places.

As for notation, often we use the underscore (_) to indicate
subscripts, so the base-10 log of something would be log_10(x);
base-2 logs would be log_2(x).

--
Stan Brown, Oak Road Systems, Cleveland, Ohio, USA
http://www.mindspring.com/~brahms/
alt.algebra.help FAQ: http://www.vex.net/~trebla/stuff/aah-faq.txt
sci.math FAQ: http://www.cs.unb.ca/~alopez-o/math-faq/mathtext/math-faq.html
Eric's Treasure Trove: http://mathworld.wolfram.com/letters/
trigonometry without tears: http://www.mindspring.com/~brahms/trig.htm
more FAQs: http://www.mindspring.com/~brahms/faqget.htm

[John Drury]

Changing the base is based on the property of logarithms that powers can be
placed as coefficients. Like:

log_3 5 = x
rearranging:
3^x = 5
taking log of both sides:
log 3^x = log 5
using that log property (can't think of proper name)
x log 3 = log 5
dividing:
x = log 5
-------
log 3

Hope this was helpful.
James Wraith wrote in message <39124B52...@usa.net>...

>I'm not sure of the notation used in this group for log base 10??? Can
>anyone help me I want to know how to use my calculator to perform
>calculations like the following:
>
>log2 (8) = 3
>or
>log 10 (100) = 2
>