JEE MATHEMATICS MCQ: TRIGONOMETRIC EQUATIONS

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Application +4 | -1

\sin \alpha, 1

and

\cos 2 \alpha

are in GP, then

\alpha

is equal to

View answer and explanation

Correct option: B

n \pi+(-1)^{n-1} \frac{\pi}{2}, n \in I

Option B (

n \pi+(-1)^{n-1} \frac{\pi}{2}, n \in I

) is correct because when

\sin \alpha, 1

and

\cos 2 \alpha

are in GP, the only possible values are when both

\sin \alpha

and

\cos 2 \alpha

are 1 or -1, leading to

\alpha = n \pi+(-1)^{n-1} \frac{\pi}{2}

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