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lim x → π 4 2 − c o s e c 2 x 1 − cot x

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Question

\[\lim_{x \to \frac{\pi}{4}} \frac{2 - {cosec}^2 x}{1 - \cot x}\] 

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Solution

\[\lim_{x \to \frac{\pi}{4}} \left[ \frac{2 - {cosec}^2 x}{1 - \cot x} \right]\]
\[ = \lim_{x \to \frac{\pi}{4}} \left[ \frac{2 - \left( 1 + \cot^2 x \right)}{1 - \cot x} \right]\]
\[ = \lim_{x \to \frac{\pi}{4}} \left[ \frac{1 - \cot^2 x}{1 - \cot x} \right]\]
\[ = \lim_{x \to \frac{\pi}{4}} \left[ \frac{\left( 1 - \cot x \right) \left( 1 + \cot x \right)}{\left( 1 - \cot x \right)} \right]\]
\[ = 1 + \cot \left( \frac{\pi}{4} \right)\]
\[ = 1 + 1\]
\[ = 2\]

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Chapter 29: Limits - Exercise 29.9 [Page 65]

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R.D. Sharma Mathematics [English] Class 11
Chapter 29 Limits
Exercise 29.9 | Q 4 | Page 65

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