Refer to the attached file.
Just replace cos2x with cos²x-sin²x
and work out.
I hope it helps u
Answer:
1 + cos(2x) = 1 + 2cos²x - 1 = 2cos²x
1 - cos(2x) = 1 - 1 + 2sin²x = 2sin²x
2cos²x/2sin²x
cot²x
d(cot²x)/dx = 2cotx × -cosec²x
= -2cotx cosec²x
