A) \[0\]
B) \[\frac{1}{2}\]
C) \[\frac{1}{\sqrt{2}}\]
D) \[\frac{\sqrt{3}}{2}\]
Correct Answer: B
Solution :
| \[\angle A=30{}^\circ \] [From eq.(1)] |
| \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\cos 2A=\cos (2\times 30{}^\circ )=\cos 60{}^\circ =\frac{1}{2}\] |
| So, option [b] is correct. |
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