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Π / 4 ∫ π / 6 C O S E C X D X - Mathematics

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Question

\[\int\limits_{\pi/6}^{\pi/4} cosec\ x\ dx\]
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Solution

\[Let\ I = \int_\frac{\pi}{6}^\frac{\pi}{4} cosec x d x . Then, \]
\[I = \int_\frac{\pi}{6}^\frac{\pi}{4} cosec\ x \frac{cosec\ x - \cot x}{cosec x - \cot x} d x\]
\[ \Rightarrow I = \int_\frac{\pi}{6}^\frac{\pi}{4} \frac{{cosec}^2\ x - cosec\ x \cot x}{cosec\ x\ - \cot x} d x\]
\[ \Rightarrow I = \left[ \log \left( cosec\ x - \cot x \right) \right]_\frac{\pi}{6}^\frac{\pi}{4} \]
\[ \Rightarrow I = \log \left( \sqrt{2} - 1 \right) - \log\left( 2 - \sqrt{3} \right)\]

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Definite Integrals
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Chapter 20: Definite Integrals - Exercise 20.1 [Page 16]

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RD Sharma Mathematics [English] Class 12
Chapter 20 Definite Integrals
Exercise 20.1 | Q 13 | Page 16

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