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Tan-1(1-cosx1+cosx),-π4<x<π4

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Question

`tan^-1 (sqrt((1 - cosx)/(1 + cosx))), - pi/4 < x < pi/4`

Sum
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Solution

Let y = `tan^-1 [sqrt((1 - cos x)/(1 + cos x))]`

= `tan^-1 [sqrt((2sin^2  x/2)/(2 cos^2  x/2))]`  ......`[(because 1 - cos x = 2sinx^2  x/2),(1 + cos x = 2 cos^2  x/2)]`

= `tan^-1 [(sin  x/2)/(cos  x/2)]`

= `tan^-1  [tan  x/2]`

∴ y = `x/2`

Differentiating both sides w.r.t. x

`"dy"/"dx" = 1/2  "d"/"dx"(x)`

= `1/2 * 1`

= `1/2`

Hence, `"dy"/"dx" = 1/2`

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Chapter 5: Continuity And Differentiability - Exercise [Page 110]

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NCERT Exemplar Mathematics Exemplar [English] Class 12
Chapter 5 Continuity And Differentiability
Exercise | Q 38 | Page 110

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