SOLUTION: Decide whether the points are the vertices of a right triangle. (2,0), (-1,-1), (1,3)

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Question 438202: Decide whether the points are the vertices of a right triangle. (2,0), (-1,-1), (1,3)
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
V%5B1%5D = <-1-2, -1-0> = <-3, -1>
V%5B2%5D = <1--1, 3--1> = <2, 4>
V%5B3%5D= <1-2, 3-0> = <-1, 3>
Take dot products:
V%5B1%5D%2AV%5B2%5D+=+-6+-+4+=+-10
V%5B2%5D%2AV%5B3%5D+=+-2+%2B+12+=+10
V%5B1%5D%2AV%5B3%5D+=+3+-+3+=+0
==> the sides of the triangle, V%5B1%5D and V%5B3%5D are perpendicular, and so the triangle is a right triangle.