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Limx→0x2cosx1-cosx is ______.

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Question

`lim_(x -> 0) (x^2 cosx)/(1 - cosx)` is ______.

Options

  • 2

  • `3/2`

  • `(-3)/2`

  • 1

MCQ
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Solution

`lim_(x -> 0) (x^2 cosx)/(1 - cosx)` is 2.

Explanation:

Given `lim_(x -> 0) (x^2 cosx)/(1 - cosx)`

= `lim_(x -> 0) (x^2 cosx)/(2sin^2  x/2)`   .....`[because 1 - cos x = 2 sin^2  x/2]`

= `lim_(x -> 0) (x^2/4 xx 4 cos x)/(2 sin^2  x/2)`

= `lim_(x -> 0 => x/2 -> 0) ((x/2)^2 * 2 cos x)/(sin^2  x/2)`

= `lim_(x/2 -> 0) ((x/2)/(sin  x/2))^2 * 2 cos x`

= 2 cos 0

= `2 xx 1`

= 2  ......`[because  lim_(x -> 0) x/sinx = 1]`

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Chapter 13: Limits and Derivatives - Exercise [Page 242]

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NCERT Exemplar Mathematics Exemplar [English] Class 11
Chapter 13 Limits and Derivatives
Exercise | Q 55 | Page 242

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