The formula for the midpoint is given by:
Using and , the point M is:
Now we can find the slope of the lines connecting M and C, and the slope of the line connecting A and B, if there slopes are the negative inverses of each other (that is, the product of their slopes is -1), then MC is perpendicular to AB.
Let be the slope of the line connecting AB
Let be the slope of the line connecting MC
Thus, MC and AB are not perpendicular