[tex]\bf \textit{terminal point }\implies
\begin{array}{lclcll}
(&1&,&-1)\\
&\uparrow &&\uparrow \\
&x&&y
\end{array}
\\\\\\
sin(\theta)=\cfrac{y}{r}
\qquad
% cosine
cos(\theta)=\cfrac{x}{r}
\qquad
% tangent
tan(\theta)=\cfrac{y}{x}\\\\
-----------------------------\\\\
\textit{so, what's the radius "r"?}\implies r^2=x^2+y^2\implies r=\sqrt{x^2+y^2}[/tex]
