$$4 { \tan }^{ 2 } \theta +6 \tan \theta -4=0$$
$\theta =\pi n_{2}+\arctan(\frac{1}{2})\text{, }n_{2}\in \mathrm{Z}$
$\theta =\pi n_{1}+\pi -\arctan(2)\text{, }n_{1}\in \mathrm{Z}$
$\theta =\pi n_{1}+\arctan(\frac{1}{2})\text{, }n_{1}\in \mathrm{Z}$
$\theta =\pi n_{2}+\pi -\arctan(2)\text{, }n_{2}\in \mathrm{Z}$
