$$sina=\frac{4}{7}; cos\phi-sec\phi; \overline{=?}$$
$t=-\sin(ϕ)\tan(ϕ)\text{, }a=2\pi n_{1}+\arcsin(\frac{4}{7})\text{, }n_{1}\in \mathrm{Z}\text{, }ϕ\neq \pi n_{3}+\frac{\pi }{2}\text{, }\forall n_{3}\in \mathrm{Z}$
$t=-\sin(ϕ)\tan(ϕ)\text{, }a=2\pi n_{2}+\pi -\arcsin(\frac{4}{7})\text{, }n_{2}\in \mathrm{Z}\text{, }ϕ\neq \pi n_{3}+\frac{\pi }{2}\text{, }\forall n_{3}\in \mathrm{Z}$
