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P Lim X → 0 Sin 3 X − Sin X Sin X

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Question

\[\lim_{x \to 0} \frac{\sin 3x - \sin x}{\sin x}\] 

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Solution

\[\lim_{x \to 0} \left[ \frac{\sin 3x - \sin x}{\sin x} \right]\]

\[= \lim_{x \to 0} \left[ \frac{2 \cos\left( \frac{3x + x}{2} \right) \sin\left( \frac{3x - x}{2} \right)}{\sin x} \right] \left[ \because \sin C - \sin D = 2\cos\left( \frac{C + D}{2} \right)\sin\left( \frac{C - D}{2} \right) \right]\]
\[ = \lim_{x \to 0} \left[ \frac{2 \cos2x . \sin x}{\sin x} \right]\]
\[ = 2\cos0\]
\[ = 2\]

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Chapter 29: Limits - Exercise 29.7 [Page 50]

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R.D. Sharma Mathematics [English] Class 11
Chapter 29 Limits
Exercise 29.7 | Q 22 | Page 50

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