What are natural logarithms used for?

1 Answer
May 15, 2015

Hello,

There are lots of answers.

1) ln is a function whose the derivative is x mapsto 1/x on ]0,+oo[.

2) ln has the property very useful : \ln(x^y) = y\ln(x). Now, you can solve the equation 3^x = 2 by using ln :
3^x = 2 <=> ln(3^x) = ln(2) <=> x ln(3) = ln(2) <=> x = ln(2)/ln(3).

3) In Chemical, you know the formula [H_3O^+] = 10^{-pH}. Therefore, ln([H_3O^+]) = -pH ln(10), and
pH = - ln([H_3O^+])/ln(10).
Remark. ln(x)/ln(10) is denoted log(x).

4) ln is used for the Richter magnitude scale to quantify the earthquake.

5) ln is used in decibel scale to quantify the noise.

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