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The number of real solutions of the equation 1+cos2x=2cos-1(cosx) in [π2,π] is ______. - Mathematics

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Question

The number of real solutions of the equation `sqrt(1 + cos 2x) = sqrt(2) cos^-1 (cos x)` in `[pi/2, pi]` is ______.

Options

  • 0

  • 1

  • 2

  • Infinite

MCQ
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Solution

The number of real solutions of the equation `sqrt(1 + cos 2x) = sqrt(2) cos^-1 (cos x)` in `[pi/2, pi]` is 0.

Explanation:

We have `sqrt(1 + cos 2x) = sqrt(2) cos^-1 (cos x)` 

⇒ `sqrt(2 cos^2x) = sqrt(2)x`        ...`[because cos^-1 (cos x) = x]`

⇒ `sqrt(2) cos x = sqrt(2)x`

⇒ cos x = x

∴ There are no solution for given equation.

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Chapter 2: Inverse Trigonometric Functions - Exercise [Page 39]

APPEARS IN

NCERT Exemplar Mathematics [English] Class 12
Chapter 2 Inverse Trigonometric Functions
Exercise | Q 36 | Page 39

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