
John R. answered 02/08/13
John R: Math, Science, and History Teacher
This problem would best be solved by graphing. Since I don't know how to do graphing (is it even possible?) in the Wyzant Answers blank, I will explain what you will see...
After plotting the three points, you will see that the line from A to B is horizontal, since they have the same y coordinate.
You will also see that the line from B to C is vertical since they have the same x coordinate.
Since line segment AB is horizontal and line segment BC is vertical, they are perpendicular.
If two legs of a triangle are perpendicular, the triangle is a right triangle.