Question

$\frac{cos ^{2}x}{4}- \frac{sin ^{2}x }{4} \geq 0$

Answer 1

-> cos²x-sin²x>=0 -> 1-sin²x-sin²x>=0-> 1>=2sin²x -> sin²x<=1/2 -> |sinx|<=√2/2 -> -π/4<=x<=π/4