May 22nd, 2016, 11:16 PM  #1 
Banned Camp Joined: May 2016 From: earth Posts: 703 Thanks: 56  What is log function?
Hello, Why we use log function in mathematics? 
May 22nd, 2016, 11:22 PM  #2 
Math Team Joined: Nov 2014 From: Australia Posts: 686 Thanks: 243 
The log function was developed to transform multiplication problems into simple addition problems. Suppose that $a$ and $b$ are horriblelooking decimals and we want to work out $ab$. If we take the logarithm of this, we get $\log (ab) = \log a + \log b$ by a simple law of logarithms. There are other reasons, such as the useful fact that $\displaystyle \int\dfrac{1}{x}\,dx = \ln x + C$. 
May 22nd, 2016, 11:47 PM  #3 
Banned Camp Joined: May 2016 From: earth Posts: 703 Thanks: 56 
PLEASE GIVE EXAMPLE MORE: a=5.7895 b=2.2358 a*b=? = 12.9441 log(ab)=log a +log b =0.76264 + 0.34943=0.26649 they are not same? 
May 23rd, 2016, 01:54 AM  #4 
Senior Member Joined: Apr 2014 From: UK Posts: 877 Thanks: 318 
a=5.7895 b=2.2358 a*b= 12.9441 log(ab)=log a +log b log(12.94416) = log (5.7895) + log (2.2358 ) 1.112074 = 0.762641 + 0.349433 They are the same. Last edited by weirddave; May 23rd, 2016 at 01:55 AM. Reason: brackets went smiley on me 
May 23rd, 2016, 02:11 AM  #5 
Math Team Joined: Nov 2014 From: Australia Posts: 686 Thanks: 243  
May 23rd, 2016, 04:51 AM  #6 
Banned Camp Joined: May 2016 From: earth Posts: 703 Thanks: 56 
I have CASIO fx 82 ms please tell how to do this?

May 23rd, 2016, 04:55 AM  #7 
Senior Member Joined: Dec 2012 From: Hong Kong Posts: 853 Thanks: 311 Math Focus: Stochastic processes, statistical inference, data mining, computational linguistics  
May 23rd, 2016, 05:05 AM  #8 
Banned Camp Joined: May 2016 From: earth Posts: 703 Thanks: 56 
Nothing is coming i have taken example of a=5 and b=3 also.. log(a*b) = log5 + log 3 = 0.698 + 0.477=1.175 so, e and e^x are coming in my calculator both are not giving 15?? 
May 23rd, 2016, 05:12 AM  #9 
Senior Member Joined: Dec 2012 From: Hong Kong Posts: 853 Thanks: 311 Math Focus: Stochastic processes, statistical inference, data mining, computational linguistics  Use the ln button. The log button in Casio calculators is the common logarithm, not the natural logarithm.

May 23rd, 2016, 05:23 AM  #10 
Banned Camp Joined: May 2016 From: earth Posts: 703 Thanks: 56 
i am not getting please tell in step.


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