Textbook Problem

Use the Distance Formula to determine the type of triangle that has these vertices:

a) $A\left(\mathrm{0,\; 0}\right), B(4, 0),$ and $C(2, 5)$

b) $D\left(\mathrm{0,\; 0}\right), E(4, 0)$, and $F\left(2, 2\sqrt{3}\right)$

c) $G(-5, 2), H(-2, 6),$ and $K(2, 3)$