$\sqrt {2 + \sqrt {2 + 2\cos 4\theta } } = $
$\sqrt {2 + \sqrt {2 + 2\cos 4\theta } } = $
- A
$\cos \theta $
- B
$\sin \theta $
- C
$2\cos \theta $
- D
$2\sin \theta $
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- [IIT 1983]
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