If the Terminal Point Determined By $\text { t }$ Is $\left( \frac { 1 } { \sqrt { 5 } } , - \frac { 2 } { \sqrt { 5 } } \right)$

Essay

If the terminal point determined by $\text { t }$ is $\left( \frac { 1 } { \sqrt { 5 } } , - \frac { 2 } { \sqrt { 5 } } \right)$ , find $\sin$ $\text { t }$ , $\cos$ $\text { t }$ and $\tan$ $\text { t }$ .