THEOREM 8-5Two nonvertical lines are perpendicular if, and only if, the slope of one is the negative reciprocal of the slope of the other line: .

To find the negative reciprocal of a number, first invert the number then change the sign. For example, to find the negative reciprocal of 4/3, you would first invert the number to get 3/4 and then change the sign (in this case from positive to negative) to get -3/4.

Two nonvertical lines are perpendicular if, and only if, the slope of one is the negative reciprocal of the slope of the other line:

can any one help me under stand this THEOREM

travisio Sep 14, 2019

#1**+1 **

Not a tough as it looks

Let's suppose that the slope of some line = a/b

This theorem says that another line will be perpendicular if it has a negative reciprocal slope

The negative reciprocal of a/b = -b/a

Farther.....if we multiply these two slope together and the result = -1.....the lines are perpendicular

So

(a/b) (-b/a) =

- (a/b) (b/a) =

- (ab) / (ba) =

- (ab) / (ab) =

- 1 ,,,,so....we see that they are truly perpendicular lines !!!!!

CPhill Sep 14, 2019