Q23 of 865 Page 19

Evaluate the following integrals:

First of all, take e^x common from the denominator, so we get

⇒

Assume e ^{- x} + 1 =t

d(e ^{- x} + 1) = dt

⇒ - e ^{- x}dx= dt

⇒ e ^{- x}dx= - dt

Substituting t and dt we get

⇒

But t =(e ^{- x} + 1)

⇒ .

Evaluate the following integrals: