$$\sec \theta = \frac { 13 } { 12 }$$
$\theta =2\pi n_{1}+\arctan(\frac{5}{12})\text{, }n_{1}\in \mathrm{Z}$
$\theta =2\pi n_{2}+2\pi -\arctan(\frac{5}{12})\text{, }n_{2}\in \mathrm{Z}$
$\theta =2\pi n_{1}+\arccos(\frac{12}{13})\text{, }n_{1}\in \mathrm{Z}$
$\theta =2\pi n_{2}+2\pi -\arccos(\frac{12}{13})\text{, }n_{2}\in \mathrm{Z}$
