C is the correct answer I worked it out
Starting from the formula

We can divide all the angles by 2 and we get

And finally

Angle x is a third quadrant angle, meaning that it is somewhere between 180 and 270. This implies that x/2 lies between 90 and 135. So, x/2 is a second quadrant angle, and its cosine is negative. This means that we can update the previous equation to

You know that

so, plug that value into the expression and you'll get cos(x/2).
The answer to your question is 
Answer:
Step-by-step explanation:
The answer is geosphere and hydrosphere
Answer:
(h,k) = (2, -3) a=4 ,b=5
Step-by-step explanation:
since the 1 is a standard equation for a right which is the left facing hyperbola with center h,k. the semi- axis A and semi is the conjuate = Axis B.