If \[\tan \alpha =\frac{1}{7},\ \tan \beta =\frac{1}{3},\]then \[\cos 2\alpha =\] [CET 1986]

If \[\tan \alpha =\frac{1}{7},\ \tan \beta =\frac{1}{3},\]then \[\cos

1.	If \[\tan \alpha =\frac{1}{7},\ \tan \beta =\frac{1}{3},\]then \[\cos 2\alpha =\] [CET 1986]
A.	\[\sin 2\beta \]
B.	\[\sin 4\beta \]
C.	\[\sin 3\beta \]
D.	None of these
Answer» C. \[\sin 3\beta \]

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If \[\tan \alpha =\frac{1}{7},\ \tan \beta =\frac{1}{3},\]then \[\cos 2\alpha =\] [CET 1986]

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