[tex]\bf ~~~~~~~~~~~~\textit{distance between 2 points}\\\\
\begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&&(~ 0 &,& -11~)
% (c,d)
&&(~ -9 &,& -12~)
\end{array}
\\\\\\
d = \sqrt{( x_2- x_1)^2 + ( y_2- y_1)^2}
\\\\\\
d=\sqrt{[-9-0]^2+[-12-(-11)]^2}
\\\\\\
d=\sqrt{(-9-0)^2+(-12+11)^2}
\\\\\\
d=\sqrt{(-9)^2+(-1)^2}\implies d=\sqrt{82}[/tex]
