Question

Помогите первую сделать!!!

Answer 1

2$cos^{2}x/2-1 \geq 0$, $cos^{2}x/2-1/2 \geq 0$,$(1+cos2 \frac{x}{2})/2-1/2 \geq 0$, $cosx \geq 0$, (0;1)