nilai dari cot(π/4+ø)xcot(π/4-ø)

TriGonoMetRi

2cos a cos b = cos (a + b) + cos (a - b)

•••
cos (π/4 + x) cos (π/4 - x)
= 1/2 (cos (2 . π/4) + cos 2x)
= 1/2 (cos 90° + cos 2x)
= 1/2 . cos 2x
= 1/2 (2 cos² x - 1)
= cos² x - 1/2 ✔