Answer:
The correct answer is the letter C. 
Explanation:
We can use the following trigonometric identity:
 (1)
 (1)
 (2)
 (2)
Solving each equation by b and equaling we have:


Let's recall that:
 
 
 
 
 
Then we have: 

 
 
 
 
 
 
Using equation (1) we can find b.
 
 
 
 
Finally, we can find a using the next equation:

 
 
 
 
Therefore, the correct answer is the letter C. 
I hope it helps you!