Answer:
Step-by-step explanation:
Given that:
Also, is in first quadrant.
To find:
Solution:
Let us have a look at the cosine of twice the angle in terms of tangent of the angle.
Suppose, we are given the value of , then the formula can be written as:
In terms of , we can re-write the formula as:
is in first quadrant, but can be in the second quadrant therefore, we have a negative value of our answer i.e. .
Therefore, the answer is: