The value of 
 .
.
Solution:
Given data:

To find the value of 

Using trigonometric identity,

Substitute 
 in the identity, we get
 in the identity, we get

1 can be written as 
 .
.
 

Do cross multiplication.
 

Denominators are same, so you can add the fractions.
 


Taking square root on both sides, we get

Option B is the correct answer.
Hence the value of 
 .
.