A) is zero
B) is positive
C) lies between \[-2\] and \[-3\]
D) is \[-3\]
Correct Answer: D
Solution :
For all x, \[\cos x\ge -1\] \[\therefore \,\,\cos A+\cos B+\cos C\ge -3\]and equality holds if \[\cos A=\cos B=\cos C=-1,\] which can be attained if \[A=\pi ,\,\,B=\pi ,\,C=-\pi \]
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