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

Equation of Parallel and Perpendicular 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.

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About Mr Mathematics

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.

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