# Equation of Parallel and Perpendicular Lines

Students learn how to find the equation of parallel and perpendicular lines in the form ax + by + c = 0.

Later, as learning progresses they link this to problems involving Pythagoras’ Theorem and ratio.

## Recapping Equation of Straight Line Graphs

At the start of the lesson students recap how to write an equation in the form ax + by + c = 0 when given its gradient and a point the line passes through.

This is a good opportunity to remind the class of how to use the equation for the gradient to write the straight line in the form ax + by + c = 0.

m=\frac{y-y_1}{x-x_1}m(x-x_1)=y-y_1

## Equation of Parallel and Perpendicular Lines

In the development phase students are asked to work through a variety of problems involving the equation of parallel and perpendicular lines.

Later, as learning progresses they challenged to work out the area of a rectangle by combining their knowledge of coordinate geometry with Pythagoras’ theorem and surds.

## Challenge Question

The challenge question takes most students about 10 minutes to complete. I set this as a plenary and encourage students to work together for peer support.

If some students struggle knowing how to get started I help them to work through the backwards by considering what is needed to find the area of each triangle.

My name is Jonathan Robinson and I am passionate about teaching mathematics. I am currently Head of Maths in the South East of England and have been teaching for over 15 years. I am proud to have helped teachers all over the world to continue to engage and inspire their students with my lessons.

## Related Lessons

4 Part Lesson
4 Part Lesson
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