Line AB
[tex]\begin{gathered} \text{slope}=m=\frac{y_2-y_1}{x_2-x_1} \\ m=\frac{4-2}{5-0}=\frac{2}{5} \end{gathered}[/tex]Line CD
[tex]m=\frac{3-8}{3-1}=\frac{-5}{2}[/tex]For lines to be perpendicular the product of their slope is equals to negative 1.
[tex]\begin{gathered} m_1m_2=-1 \\ \frac{2}{5}\times-\frac{5}{2}=-\frac{10}{10}=-1 \end{gathered}[/tex]Therefore, the lines are perpendicular.
