Question

If cos⁻¹x – cos⁻¹
y/2
= α , where -1 ≤ x ≤ 1, – 2 ≤ y ≤ 2, x ≤
y/2, then for all x, y, 4x² – 4xy cos α + y²
is equal to (A) 4 sin²α - 2x²y²
(B) 4 cos²α + 2x²y²
(C) 2 sin²α (D) 4 sin²α

Answer 1

Hey mate!!

maybe the answer is

c)

hope it's right