Use this activity to investigate perpendicular lines (that is, lines that are at 90 degrees to each other).
Below is a red line, with the gradient of the line calculated. Can you work out how the gradient was calculated? (Hint: look at the pink triangle)
The blue line is perpendicular to the red line through the green point. The green triangle shows the gradient of the blue line.
Select the red points and move them to change the gradient of the red line. What happens to the gradient of the blue line? Explain why this happens.
How are the gradients of the red line and blue line related to each other?
Select the green points to change the green triangle.
Think about how the gradient is calculated from the information given.
This investigation into the gradients of perpendicular lines would make an excellent homework to be discussed in the following lesson. Have every student explore the relationship between the gradients until they can explain clearly whay the relationship is. Alternatively, use this as an activity in a computer based lesson, or at the front and have a whole class discussion of the result. Goes well with the activity on parallel lines.
If you have found interactive-maths.com a useful website, then please support it by making a donation using the button opposite.