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Trigonometrical Equations
normal
સમીકરણ $\sin 2\theta + \cos 2\theta = - \frac{1}{2},\theta \in \left( {0,\frac{\pi }{2}} \right)$ ના ઉકેલોની સંખ્યા મેળવો,
A
$0$
B
$1$
C
$2$
D
$3$
Solution

${\sin 2 \theta+\cos 2 \theta=-\frac{1}{2}} $
${\sin \left(\frac{\pi}{4}+2 \theta\right)=-\frac{1}{2 \sqrt{2}}} $
${\text { Let } \frac{\pi}{4}+2 \theta=\alpha} $
${\sin \alpha=-\frac{1}{2 \sqrt{2}}} $
${\therefore \text { only one solution }}$
Standard 11
Mathematics