1.

If \[\sqrt{x}+\frac{1}{\sqrt{x}}=2\cos \theta ,\]then \[{{x}^{6}}+{{x}^{-6}}=\] [Karnataka CET 2003]

A. \[2\cos 6\theta \]
B. \[2\cos 12\theta \]
C. \[2\cos 3\theta \]
D. \[2\sin 3\theta \]
Answer» C. \[2\cos 3\theta \]


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