If $\sin \theta=\sin 15^{\circ}+\sin 45^{\circ}$, where $0^{\circ} < \theta < 180^{\circ}$, then $\theta=$
If $\sin \theta=\sin 15^{\circ}+\sin 45^{\circ}$, where $0^{\circ} < \theta < 180^{\circ}$, then $\theta=$
- $75^{\circ}$
- $150^{\circ}$
- $45^{\circ}$
- $60^{\circ}$
Solution
$\begin{aligned} \text { Given } \sin \theta &=\sin 15^{\circ}+\sin 45^{\circ} \\ &=2 \sin \left(\frac{15^{\circ}+45^{\circ}}{2}\right) \cos \left(\frac{15^{\circ}-45^{\circ}}{2}\right) \\ &=2 \sin 30^{\circ} \cos 15^{\circ}=2 \times \frac{1}{2} \cos 15^{\circ} \\ \sin \theta &=\cos 15^{\circ} \Rightarrow \sin \theta=\sin \left(90^{\circ}-15^{\circ}\right) \Rightarrow \theta=75^{\circ} \end{aligned}$
Asked in: MHT CET 2020 (20 Oct Shift 1)
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