2 ^2 - 2 ^2 = 1, then = .......^o - Vidyadip

MCQ

$2{\cos ^2}\theta - 2{\sin ^2}\theta = 1$, then $\theta =$ .......$^o$

A
$15$
✓
$30$
C
$45$
D
$60$

✓

Answer

Correct option: B.

$30$

b
(b) $2{\cos ^2}\theta - 2{\sin ^2}\theta = 1$

==> $2\cos 2\theta = 1$

==> $\cos 2\theta = \frac{1}{2} = \cos {60^o}$

==> $2\theta = {60^o}$

$\Rightarrow \theta = {30^o}$.

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