If tan alpha = ( 1)/( 7 ), tan beta = ( ...

If `tan alpha = ( 1)/( 7 ), tan beta = ( 1)/( 3)`, then `cos 2 alpha=`

A

`sin 2 beta`

B

`sin 4 beta`

C

`sin 3 beta`

D

`cos 2 beta`

Verified by Experts

The correct Answer is:

B

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