JEE MATHEMATICS MCQ: SEQUENCE OF SERIES

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Application +4 | -1

\cos (x-y), \cos x

and

\cos (x+y)

are in HP, then

\cos x \sec \left(\frac{y}{2}\right)

is equal to

View answer and explanation

Correct option: A

\pm \sqrt{2}

Option A (

\pm \sqrt{{2}}

) is correct because by using the Harmonic Progression (HP) condition and trigonometric identities, we can derive that

\cos x \sec \left(\frac{{y}}{{2}}\right) = \pm \sqrt{{2}}

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