Answer:


Explanation:
Cosine Of A Sum Of Angles
The cosine of the sum of angles can be expressed in terms of the individual angles as follows

The cosine of the subtraction of angles is

Since we have

We can see it's equivalent to the cosine of the subtraction of angles, thus

Completing the equation we have

We know

And also

So we have two possible solutions


Thus, the first solution is


And the second solution is

