Use vectors to show that A(2,-1,1), B(3,2,-1), and C(7,0,-2) are vertices of a right triangle.
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Originally Posted by jmedsy Use vectors to show that A(2,-1,1), B(3,2,-1), and C(7,0,-2) are vertices of a right triangle. $\displaystyle AB = (1,3,-2)$ $\displaystyle BC = (4,-2,-1)$ $\displaystyle AB \cdot BC = 4 - 6 + 2 = 0$ what's that tell you?
ab and bc are orthogonal. there is a right angle at vertex b
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