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Evaluate the following limit. limx→0cos2x-1cosx-1 - Mathematics

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Question

Evaluate the following limit.

`lim_(x -> 0) (cos 2x -1)/(cos x - 1)`

Sum

Solution

`lim_(x → 0) (cos 2x - 1)/(cos x - 1)`

= `lim_(x → 0) (1 - 2 sin^2 x - 1)/(cosx - 1)`

= `lim_(x → 0) (2sin^2 x)/(1 - cosx)`

= `lim_(x → 0) (2(1 - cosx)(1 + cosx))/(1 - cosx)`

= `lim_(x → 0) 2(1 + cosx)`

= 2(1 + cos 0)

= 2 × 2 

= 4

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Chapter 13: Limits and Derivatives - Exercise 13.1 [Page 302]

APPEARS IN

NCERT Mathematics [English] Class 11
Chapter 13 Limits and Derivatives
Exercise 13.1 | Q 17 | Page 302

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