e 1 $. Not simultaneous. Try to find $ x $ such that $ \sin 3x \sin x = 1 $. This requires both $ |\sin 3x| = 1 $ and $ |\sin x| = 1 $, and same sign. But suppose $ \sin x = 1 \Rightarrow x = rac\pi2 $, then $ \sin 3x = \sin\left(rac3\pi2