In Example 7(a), change B(6, 0) to B(−4,−2).

Data from Example 7(a)

Show that the line segments joining A(−5, 3), B(6, 0), and C(5, 5) form a right triangle. See Fig. 21.12.

If these points are vertices of a right triangle, the slopes of two of the sides must be negative reciprocals. This would show perpendicularity. These slopes are

We see that the slopes of AC and BC are negative reciprocals, which means
From this we conclude that the triangle is a right triangle.

MAB = 3-0 -5-6 = 3 11 MAC = 3-5 -5-5 = m BC = 0 5 6-5 || = -5