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Evaluate: limx→01-cosmx1-cosnx

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Question

Evaluate: `lim_(x -> 0) (1 - cos mx)/(1 - cos nx)`

Sum
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Solution

Given that `lim_(x -> 0) (1 - cos mx)/(1 - cos nx)`

= `lim_(x -> 0)  ((2 sin^2  m/2 x)/(2 sin^2  n/2 x))`

= `lim_(x -> 0) ((sin  m/2 x)/(sin  n/2 x))`

= `(lim_(x -> 0) ((sin  m/2 x)/(m/2 x) xx m/2 x)^2)/(lim_(x -> 0)  ((sin  n/2 x)/(sin  n/2 x) xx n/2 x)^2)`

= `(1 * m^2/4 x^2)/(1 * n^2/4 x^2)`  ......`[because  lim_(x -> 0)  sinx/x = 1]`

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Chapter 13: Limits and Derivatives - Exercise [Page 240]

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NCERT Exemplar Mathematics [English] Class 11
Chapter 13 Limits and Derivatives
Exercise | Q 19 | Page 240

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