JEE MATHEMATICS MCQ: SEQUENCE OF SERIES

1 Easy

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Analyzing +4 | -1

Suppose

\theta

and

\phi(\neq 0)

are such that

\sec (\theta+\phi), \sec \theta

and

\sec (\theta-\phi)

are in A.P. If

\cos \theta=k \cos \left(\frac{\phi}{2}\right)

for some

k

, then

k

is equal to

View answer and explanation

Correct option: A

\pm \sqrt{2}

Option A (

\pm \sqrt{2}

) is correct because by using the A.P. condition and trigonometric identities, we can derive that

k = \pm \sqrt{2}

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