A) 3
B) \[-2\]
C) 2
D) \[-3\]
E) \[-1\]
Correct Answer: E
Solution :
\[\cos 2\alpha +\cos 2\beta +\cos 2\gamma \]\[=2({{\cos }^{2}}\alpha +{{\cos }^{2}}\beta +{{\cos }^{2}}\gamma )-3\] \[=2-3=-1\] \[(\because {{\cos }^{2}}\alpha +{{\cos }^{2}}\beta +{{\cos }^{2}}\gamma =1)\]
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