Integral Calculus Question 485

Question: The value of $ \int_{{}}^{{}}{\frac{e^{x}}{e^{x}+1}},dx $ is

[Pb. CET 2000]

Options:

A) $ e^{x}+c $

B) $ (e^{x}+1)+c $

C) $ \log (e^{x}+1)+c $

D) None of these

Show Answer

Answer:

Correct Answer: C

Solution:

Put $ e^{x}+1=t\Rightarrow e^{x}dx=dt $
$ \therefore $ $ \int_{{}}^{{}}{\frac{e^{x}}{e^{x}+1}dx=\int_{{}}^{{}}{\frac{dt}{t}=\log t+c=\log (e^{x}+1)+c}} $ .