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If sec ( theta - alpha ) , sec theta , ...

If ` sec ( theta - alpha ) , sec theta , sec ( theta + alpha ) ` are in A.P. then ` cos theta =`

A

`cos alpha `

B

`cos alpha //2`

C

`2 cos alpha //2`

D

`sqrt(2) cos alpha //2 `

Text Solution

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The correct Answer is:
D
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DIPTI PUBLICATION ( AP EAMET)-TRIGONOMETRIC RATIOS AND IDENTITIES -EXERCISE 1 C ( MULTIPLE AND SUBMULTIPLE ANGLES )
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