[tex]\Large\boxed{\begin{array}{l}\sf Seja~A(x_A,y_A)~e~B(x_B,y_B)\\\sf o~coeficiente~angular~da~reta~\\\sf que~passa~por~A~e~B~\acute e\\\sf m=\dfrac{y_B-y_A}{x_B-x_A}\end{array}}[/tex]
[tex]\boxed{\begin{array}{l}\sf P'(3,2)~P''(3,-2)\\\sf m=\dfrac{-2-2}{3-3}\\\sf m=\dfrac{-4}{0}\implies coeficiente~angular~inexistente\end{array}}[/tex]
