√ {2 + √ {2 + 2cos 4θ } } =

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3.Trigonometrical Ratios, Functions and Identities

easy

$\sqrt {2 + \sqrt {2 + 2\cos 4\theta } } = $

A

$\cos \theta $

B

$\sin \theta $

C

$2\cos \theta $

D

$2\sin \theta $

Solution

(c) $\sqrt {2 + \sqrt {2 + 2\cos 4\theta } } $

$=\sqrt {2 + \sqrt {2.2{{\cos }^2}2\theta } } $

$ = \sqrt {2 + 2\cos 2\theta }$

$= \sqrt {4{{\cos }^2}\theta } $

$= 2\cos \theta $.

Standard 11

Mathematics

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