1 câu trả lời
Hàm số : \(\sin2x=\cos x \)
\(\Leftrightarrow \sin 2x=\sin \left({\dfrac{\pi}{2}-x}\right)\) \(\Leftrightarrow \left\{ \begin{array}{l} 2x=\dfrac{\pi}{2}-x+k2\pi \\ 2x=\pi-\left({\dfrac{\pi}{2}-x}\right)+k2\pi \end{array} \right .(k\in\mathbb Z)\) \(\Leftrightarrow \left\{ \begin{array}{l} x=\dfrac{\pi}{6}+k\dfrac{2\pi}{3} \\ x=\dfrac{\pi}{2}+k2\pi \end{array} \right .(k\in\mathbb Z).\)
