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Find the principal value of the following: cos-1(-1/sqrt2) - Mathematics

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Question

Find the principal value of the following:

`cos^(-1) (-1/sqrt2)`

Sum
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Solution

Let `cos^(-1)(-1/sqrt2)` = y

Then cos y = `- 1/sqrt2 = -cos (pi/4) = cos(pi - pi/4) = cos((3pi)/4)`

We know that the range of the principal value branch of cos−1 is [0, π].

Where `(3pi)/4 ∈ [0, pi]`

`cos ((3pi)/4) = - 1/sqrt2`

Therefore, the principal value of `cos^(-1) (-1/sqrt2)` is `(3pi)/4`.

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Chapter 2: Inverse Trigonometric Functions - Exercise 2.1 [Page 42]

APPEARS IN

NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 2 Inverse Trigonometric Functions
Exercise 2.1 | Q 9 | Page 42

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