Author Topic: calculating the natural logarithm of an arbitrary number (Read 3887 times)

aeTIos · « **on:** December 23, 2011, 09:09:29 am »

Hello guys,

As stated in the subject. I can't use this:

since that only works for x=-1 through x=1...

Who knows another summation/computation algorithm? Thanks!

bsl · « **Reply #1 on:** December 23, 2011, 09:52:03 am »

Quote from: aeTIos on December 23, 2011, 09:09:29 am

Hello guys,

As stated in the subject. I can't use this: since that only works for x=-1 through x=1...

Who knows another summation/computation algorithm? Thanks!

(x-1)/(x+1) +1/3 * [(x-1)/(x+1)]^3 + 1/5 * [(x-1)/(x+1)]^5 + 1/7 * [(x-1)/(x+1)]^7 .....
for x > 0
There are shortcuts on a calculator to do this.

Adriweb · « **Reply #2 on:** December 23, 2011, 12:52:44 pm »

Taylor it

(oh, well, bsl actually wrote directly an approximation...)

phenomist · « **Reply #3 on:** January 18, 2012, 02:31:34 am »

Also, ln(x)=-ln(1/x)

If x is not between -1 and 1, take its reciprocal. (I'd also like to note that ln(negative number) is a bad idea.)

Author Topic: calculating the natural logarithm of an arbitrary number (Read 3887 times)

aeTIos

calculating the natural logarithm of an arbitrary number

bsl

Re: calculating the natural logarithm of an arbitrary number

Adriweb

Re: calculating the natural logarithm of an arbitrary number

phenomist

Re: calculating the natural logarithm of an arbitrary number