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1 ∫ − 1 1 X 2 + 2 X + 5 D X

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Question

\[\int\limits_{- 1}^1 \frac{1}{x^2 + 2x + 5} dx\]
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Solution

\[Let\ I = \int_{- 1}^1 \frac{1}{x^2 + 2x + 5} d x . Then, \]
\[ I = \int_{- 1}^1 \frac{1}{\left( x^2 + 2x + 1 \right) + 4} d x\]
\[ \Rightarrow I = \int_{- 1}^1 \frac{1}{\left( x + 1 \right)^2 + 2^2} d x\]
\[ \Rightarrow I = \frac{1}{2} \left[ \tan^{- 1} \frac{\left( x + 1 \right)}{2} \right]_{- 1}^1 \]
\[ \Rightarrow I = \frac{1}{2}\left( \tan^{- 1} 1 - \tan^{- 1} 0 \right)\]
\[ \Rightarrow I = \frac{1}{2}\left( \frac{\pi}{4} \right)\]
\[ \Rightarrow I = \frac{\pi}{8}\]

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Chapter 19: Definite Integrals - Exercise 20.1 [Page 17]

APPEARS IN

R.D. Sharma Mathematics Volume 1 and 2 [English] Class 12
Chapter 19 Definite Integrals
Exercise 20.1 | Q 44 | Page 17

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