A) 9
B) 3
C) 5
D) 7
Correct Answer: D
Solution :
\[2\cos 2x\cos x+2\cos 3x\cos x=0\] \[\Rightarrow \]\[2\cos x(\cos 2x+\cos 3x)=0\] \[2\cos x2\cos 5x/2\cos x/2=0\] \[x=\frac{\pi }{2},\frac{3\pi }{2},\pi ,\frac{3\pi }{5},\frac{7\pi }{5},\frac{9\pi }{5}\] 7 SolutionsYou need to login to perform this action.
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