[tex]\Rightarrow sin^2x=t \in (0;1)[/tex], chọn [tex]t=\dfrac{1}{2} \Rightarrow cos2x=0 \Rightarrow x=\dfrac{\pi}{4}+\dfrac{k\pi}{2}[/tex]
[tex]\Rightarrow 0 \leq \dfrac{\pi}{4}+\dfrac{k\pi}{2}\leq 50\pi\Rightarrow 0 \leq k \leq 99[/tex]
Có 100 nghiệm