One branch of cos–1 other than the principal value branch corresponds to

(A)   [π/2, 3π/2]

(B) [π, 2π] - {3π/2}

(C) (0, π)

(D) [2π, 3π]

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2 Answers

(D) is the correct answer.

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

Also, we know that the period of cosθ is 2π.

Now, let θ \(\in\) [2π, 3π]

And cos(2π – θ) = cos θ

Thus, 2π – θ \(\in\) [0, π].

Therefore, [2π, 3π] corresponds to the principal value branch for cos-1x.

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