cos^-1 [1/2.x^2 + √(1- x^2).√(1 - (x^2/4))] = cos^-1 (x/2) - cos^-1 (x), is true if:



A)|x| ≤ 1

B) x is a real number

C) 0 ≤ x ≤ 1

D)-1 ≤ x ≤ 0