$$4\sin\ \theta-2cos\theta=3$$
$\theta =2\pi n_{1}+\arcsin(\frac{\sqrt{11}+6}{10})\text{, }n_{1}\in \mathrm{Z}$
$\theta =2\pi n_{2}-\arcsin(\frac{6-\sqrt{11}}{10})+\pi \text{, }n_{2}\in \mathrm{Z}$
