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If 5 cos 2 theta +2 cos^2 (theta/2)+1=0,...

If `5 cos 2 theta +2 cos^2 (theta/2)+1=0`, when `(0 ltthetalt pi)`, then the values of `theta` are :

A

`pi/3 +- pi`

B

`pi/3, cos^-1 (3//5)`

C

`cos^-1 (3//5) +- pi`

D

`pi/3, pi- cos^-1 (3/5)`.

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MODERN PUBLICATION-TRIGNOMETRY-EXERCISE
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