Chapter 9 Quadratic Relations and Conic Sections - 9.1 Apply the Distance and Midpoint Formulas - 9.1 Exercises - Skill Practice - Page 617: 22

isosceles

The distance formula from $P_1(x_1,y_1)$ to $P_2(x_2,y_2)$ is $d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$. Hence here: $a=\sqrt{(-5-0)^2+(0-6)^2}=\sqrt{61}$, $b=\sqrt{(-5-5)^2+(0-0)^2}=\sqrt{100}=10$, $c=\sqrt{(0-5)^2+(6-0)^2}=\sqrt{61}$, thus the triangle is isosceles.