[tex]\\ \sf\longmapsto \sqrt{(x_2-x_1)^2+(y_2-y_1)^2}[/tex]
[tex]\\ \sf\longmapsto \sqrt{(-9-0)^2+(1-10)^2}[/tex]
[tex]\\ \sf\longmapsto \sqrt{(-9)^2+(-9)^2}[/tex]
[tex]\\ \sf\longmapsto \sqrt{81+81}[/tex]
[tex]\\ \sf\longmapsto \sqrt{162}[/tex]
[tex]\\ \sf\longmapsto 12.42[/tex]
