Solve , .
After a few steps, I obtained
or
From , I obtained the solution . Is is a solution?
Did you even bother to look at the graph?
$\sin{x} = 0 \implies x = k\pi$, which are not valid solutions.
the Wolfram graph does not show the point discontinuities on the x-axis at integer multiples of $\pi$
The valid solutions are where $x = \arccos\left(-\dfrac{2}{3}\right)$