Question

A triangle has vertices A(-1,3,4) , B(3,-1,1,) and C(5,1,1). Prove that it is right-angled?

Answer 1

move them so one of the points hits the origin; which just amounts to subtracting the value of one point from the other two

Answer 2

A(-1,3,4) , B(3,-1,1,) and C(5,1,1)
1-3-4 1-3-4 1-3-4
--------------------------------
0,0,0 4,-4,-3 6,-2,-3

if B.C = 0, its a right triangle; otherwise try it again from a different point

Answer 3

another method is to get all the lengths between each point and pythag it to check