[tex]\bf \begin{array}{clclll}
(-6&,&-8)\\
x&&y\\
a&&b
\end{array}\qquad c^2=a^2+b^2\implies c=\sqrt{a^2+b^2}
\\\\\\
c=\sqrt{(-6)^2+(-8)^2}\implies c=\sqrt{100}\implies c=10\impliedby
\begin{array}{llll}
c\ is\ never\\
negative
\end{array}
\\\\\\
sin(\theta)=\cfrac{opposite}{hypotenuse}\implies sin(\theta)=\cfrac{-8}{10}
\\\\\\
sin(\theta)=-\cfrac{4}{5}[/tex]
