$$\cos \theta \tan \theta = \frac { 3 } { 5 }$$
$\theta =2\pi n_{2}+\arctan(\frac{3}{4})\text{, }n_{2}\in \mathrm{Z}$
$\theta =2\pi n_{1}+\pi -\arctan(\frac{3}{4})\text{, }n_{1}\in \mathrm{Z}$
$\theta =2\pi n_{1}+\arcsin(\frac{3}{5})\text{, }n_{1}\in \mathrm{Z}$
$\theta =2\pi n_{2}+\pi -\arcsin(\frac{3}{5})\text{, }n_{2}\in \mathrm{Z}$
