Use this activity to investigate parallel lines.
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 parallel to the red line through the blue 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 blue point to change the position of the blue line.
What can you say about the gradient of parallel lines?
This investigation into the gradients of parallel 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 perpendicular lines.
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