Definite Integration Question 96

Question: The function $ L(x)=\int_1^{x}{\frac{dt}{t}} $ satisfies the equation

[IIT 1996; DCE 2001]

Options:

A) $ L(x+y)=L(x)+L(y) $

B) $ L( \frac{x}{y} )=L(x)+L(y) $

C) $ L(xy)=L(x)+L(y) $

D) None of these

Show Answer

Answer:

Correct Answer: C

Solution:

Given function $ L(x)=\int_1^{x}{\frac{1}{t}dt=[\log t]_1^{x}}=\log x-\log 1 $

therefore $ L(x)=\log x $ ,

Hence $ L(xy)=L(x)+L(y) $ .