Sos mng oi!!!

Bài 2: 1) $\sqrt{2}\cos 2x - 1 = 0$ $\cos 2x = \frac{1}{\sqrt{2}} = \frac{\sqrt{2}}{2}$ $2x = \pm \frac{\pi}{4} + k2\pi$, $k \in \mathbb{Z}$ $x = \pm \frac{\pi}{8} + k\pi$, $k \in \mathbb{Z}$ 2) $\sin x = \cos 3x$ $\sin x = \sin (\frac{\pi}{2} - 3x)$ $x = \frac{\pi}{2} - 3x + k2\pi$ hoặc $x = \pi - (\frac{\pi}{2} - 3x) + k2\pi$, $k \in \mathbb{Z}$ $x = \frac{\pi}{8} + k\frac{\pi}{2}$ hoặc $x = -\frac{\pi}{4} + k\pi$, $k \in \mathbb{Z}$ 3) $\cos(x + \frac{\pi}{3}) + \sin(3x + \frac{\pi}{4}) = 0$ $\cos(x + \frac{\pi}{3}) = -\sin(3x + \frac{\pi}{4})$ $\cos(x + \frac{\pi}{3}) = \sin(-3x - \frac{\pi}{4})$ $x + \frac{\pi}{3} = -3x - \frac{\pi}{4} + k2\pi$ hoặc $x + \frac{\pi}{3} = \pi - (-3x - \frac{\pi}{4}) + k2\pi$, $k \in \mathbb{Z}$ $x = -\frac{7\pi}{16} + k\frac{\pi}{2}$ hoặc $x = \frac{\pi}{16} + k\pi$, $k \in \mathbb{Z}$ 4) $\tan 2x = \cot(x + \frac{\pi}{4})$ $\tan 2x = \tan(\frac{\pi}{2} - (x + \frac{\pi}{4}))$ $\tan 2x = \tan(\frac{\pi}{4} - x)$ $2x = \frac{\pi}{4} - x + k\pi$, $k \in \mathbb{Z}$ $x = \frac{\pi}{12} + k\frac{\pi}{3}$, $k \in \mathbb{Z}$ 5) $\sin x = \sqrt{3}\cos x$ $\tan x = \sqrt{3}$ $x = \frac{\pi}{3} + k\pi$, $k \in \mathbb{Z}$ 6) $\tan^2(\frac{\pi}{3} - 2x) - 3 = 0$ $\tan^2(\frac{\pi}{3} - 2x) = 3$ $\tan(\frac{\pi}{3} - 2x) = \pm \sqrt{3}$ $\frac{\pi}{3} - 2x = \pm \frac{\pi}{3} + k\pi$, $k \in \mathbb{Z}$ $x = \pm \frac{\pi}{6} + k\frac{\pi}{2}$, $k \in \mathbb{Z}$