# Perpendicular lines and their Gradients

- Author:
- Lew W. S.

- Topic:
- Angles, Straight Lines

In thiis activity, you will see the relationship between 2 perpendicular lines and their gradients.
For simplicity the equations of the lines you draw have already been given automatically.
Use the checkboxes to view or hide values of coordinates, equations and gradient

Drag points A, B for the first line.
The line CD has been set to be perpendicular to line AB
Observe the gradient of line AB, ie. m1 and gradient of line CD ie m2.
Note the product of m1 and m2.
Is the product always the same, no matter how we draw line AB,
as long as line CD is perpendicular to AB?