giúp mình giải bài: sin10x – cos6x = căn 3(sin6x – cos10x) 18/09/2021 Bởi Rylee giúp mình giải bài: sin10x – cos6x = căn 3(sin6x – cos10x)
$\begin{array}{l} \sin 10x – \cos 6x = \sqrt 3 \left( {\sin 6x – \cos 10x} \right)\\ \Leftrightarrow \sin 10x + \sqrt 3 \cos 10x = \sqrt 3 \sin 6x + \cos 6x\\ \Leftrightarrow \frac{1}{2}\sin 10x + \frac{{\sqrt 3 }}{2}\cos 10x = \frac{{\sqrt 3 }}{2}\sin 6x + \frac{1}{2}\cos 6x\\ \Leftrightarrow \sin \left( {10x + \frac{\pi }{3}} \right) = \sin \left( {6x + \frac{\pi }{6}} \right)\\ \Leftrightarrow \left[ \begin{array}{l} 10x + \frac{\pi }{3} = 6x + \frac{\pi }{6} + k2\pi \\ 10x + \frac{\pi }{3} = \pi – 6x – \frac{\pi }{6} + k2\pi \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l} 4x = – \frac{\pi }{6} + k2\pi \\ 16x = \frac{\pi }{2} + k2\pi \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} x = – \frac{\pi }{{24}} + \frac{{k\pi }}{2}\\ x = \frac{\pi }{{32}} + \frac{{k\pi }}{8} \end{array} \right. \end{array}$ Bình luận
$\begin{array}{l}
\sin 10x – \cos 6x = \sqrt 3 \left( {\sin 6x – \cos 10x} \right)\\
\Leftrightarrow \sin 10x + \sqrt 3 \cos 10x = \sqrt 3 \sin 6x + \cos 6x\\
\Leftrightarrow \frac{1}{2}\sin 10x + \frac{{\sqrt 3 }}{2}\cos 10x = \frac{{\sqrt 3 }}{2}\sin 6x + \frac{1}{2}\cos 6x\\
\Leftrightarrow \sin \left( {10x + \frac{\pi }{3}} \right) = \sin \left( {6x + \frac{\pi }{6}} \right)\\
\Leftrightarrow \left[ \begin{array}{l}
10x + \frac{\pi }{3} = 6x + \frac{\pi }{6} + k2\pi \\
10x + \frac{\pi }{3} = \pi – 6x – \frac{\pi }{6} + k2\pi
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
4x = – \frac{\pi }{6} + k2\pi \\
16x = \frac{\pi }{2} + k2\pi
\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}
x = – \frac{\pi }{{24}} + \frac{{k\pi }}{2}\\
x = \frac{\pi }{{32}} + \frac{{k\pi }}{8}
\end{array} \right.
\end{array}$