Mark the Correct alternative in the following:

If then cos 2α is equal to

Given and

Now to find the value of cos 2α

[By using ]

[as is given]

Hence

The same value is obtained for sin 4β.

[By sin 2x = 2 sinx cosx]

[using and ]

We have

As

As the value of cos 2α and sin 4α are the same, the answer is option B.