Let the three points be A(-2, 5), B(3, - 4) and C(7, 10).
Then AB2 = (3 + 2)2 + (-4 - 5)2 = 106
BC2 = (7 - 3)2 + (10 + 4)2 = 212
AC2 = (7 + 2)2 + (10 - 5)2 = 106
We see that BC2 = AB21 + AC2
212 = 106 + 106
212 = 212
∠A = 900
Thus, ABC is a right triangle, right angled at A.
