\[\begin{array}{l} \sin 6x - \sin 4x = \sin 8x - \sin 2x \hfill \\ \sin x - \sin y = 2\sin \frac{{x - y}}{2}\cos \frac{{x + y}}{2} \hfill \\ 2\sin x\cos 5x = 2\sin 3x\cos 5x \Leftrightarrow \left[ \begin{array}{l} \cos 5x = 0 \hfill \\ \sin x = \sin 3x \hfill \\ \end{array} \right. \hfill \\ \end{array}\]