sin3x = cos x =sin(\frac{\pi}{2}-x)\\ \\ \therefore 3x = n\pi + (-1)^n (\frac {\pi}{2} - x) $ $(n = 0, 1, 2, . . .) \\ \\ $For n = 0, 1, 2, 3, 4, 5, 6 we get respectively: $ \\ \\ x = \frac {\pi}{8}, \frac{\pi}{4}, \frac {5 \pi}{8}, \frac {\5\pi}{4}, \frac {9\pi}{8}, \frac {9\pi}{4} $ (outside...