A) \[\text{80 }\!\!{}^\circ\!\!\text{ }\]
B) \[\text{70 }\!\!{}^\circ\!\!\text{ }\]
C) \[\text{60 }\!\!{}^\circ\!\!\text{ }\]
D) \[50{}^\circ \]
Correct Answer: C
Solution :
\[\mu =\frac{\sin \frac{A+\delta }{2}}{\sin \frac{A}{2}}=\frac{\sin \frac{A+A}{2}}{\sin \frac{A}{2}}=\frac{\sin A}{\sin \frac{A}{2}}\] \[=\frac{2\sin \frac{A}{2}\cos \frac{A}{2}}{\sin \frac{A}{2}}=2\cos \frac{A}{2}\] So, \[\sqrt{3}=2\cos \frac{A}{2}\Rightarrow \frac{\sqrt{3}}{2}=\cos \frac{A}{2}\Rightarrow A={{60}^{o}}\]
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