$$2\ \sin^{2}x-7\ \sin\ x+3=0$$
$x=2\pi n_{1}+\frac{\pi }{6}\text{, }n_{1}\in \mathrm{Z}$
$x=2\pi n_{1}+\frac{5\pi }{6}\text{, }n_{1}\in \mathrm{Z}$
