Đáp án:
Giải thích các bước giải:
`sin\ \frac{x}{2}=-\frac{\sqrt{2}}{2}`
`⇔ sin\ \frac{x}{2}=sin\ -\frac{\pi}{4}`
`⇔` \(\left[ \begin{array}{l} \dfrac{x}{2}=-\dfrac{\pi}{4}+k2\pi\ (k \in \mathbb{Z})\\\dfrac{x}{2}=\pi+\dfrac{\pi}{4}+k2\pi\ (k \in \mathbb{Z})\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l} x=-\dfrac{\pi}{2}+k4\pi\ (k \in \mathbb{Z})\\x=\dfrac{5\pi}{2}+k4\pi\ (k \in \mathbb{Z})\end{array} \right.\)
