1 câu trả lời
\(\begin{array}{l} pt \Leftrightarrow \left[ \begin{array}{l} 2\cos x + \sqrt 3 = 0\\ 2\cos 2x - 3\sin x - 2 = 0 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} \cos x = - \dfrac{{\sqrt 3 }}{2}\\ 2\left( {1 - 2{{\sin }^2}x} \right) - 3\sin x - 2 = 0 \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l} \cos x = - \dfrac{{\sqrt 3 }}{2}\\ 4{\sin ^2}x + 3\sin x = 0 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} \cos x = - \dfrac{{\sqrt 3 }}{2}\\ \sin x = 0\\ \sin x = - \dfrac{3}{4} \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} x = \pm \dfrac{{3\pi }}{4} + k2\pi \\ x = k\pi \\ x = \arcsin \left( { - \dfrac{3}{4}} \right) + k2\pi \\ x = \pi - \arcsin \left( { - \dfrac{3}{4}} \right) + k2\pi \end{array} \right. \end{array}\)