Subject  Maths  Key stage  4 

Topic Area  Number and algebra: Pythagoras’ theorem  Programme of study links 

Objectives  To understand Pythagoras' theorem and how it can be used to calculate the hypotenuse 
1.3b, 2.2, 3.2c 
Lesson plan context  This lesson uses largescale demonstrations and a dynamic reallife context to engage students and reinforce the relevance of the theory behind the theorem of Pythagoras. It begins with a review of the terminology of rightangled triangles and clear visual explanations of how Pythagoras’ theorem can be expressed geometrically and algebraically. The formula is made relevant by its application to a real context and its use in calculating the length of the hypotenuse is demonstrated. The new concepts are reinforced with practice questions and reviewed using the ‘Tick or trash’ feature. 

Teaching context  Class and group work. The lesson can be carried out using video clips and a projector/whiteboard. Two worksheets are provided to help consolidate the students’ understanding of the key mathematical concepts covered in this lesson plan. These worksheets can be used alongside course materials on this topic. 
Notes on timing  This lesson will cover 12 hours depending on the ability level of the students. Lowerability students may need more time to develop their understanding of the principles and application of Pythagoras’ theorem. If time is limited, the worksheet in the Main section could be carried out as an alternative homework activity and the plenary activity could be used as a starter in a followup lesson. For higherability students who take less time to grasp the key ideas, the lesson could be extended by incorporating the extension activities in the classroom. 
Key question  How can Pythagoras’ theorem be useful? 

Starter  Start the lesson with the clip Pythagoras’ theorem (1): introduction, which provides an overview of rightangled triangles and two largescale demonstrations of the theorem of Pythagoras. The prompt questions can be used to focus the students’ attention and then stimulate discussion to establish what they already know about this topic. Students could be presented with triangles in a variety of orientations and discuss how they can identify the hypotenuse. They could also try identifying rightangled triangles within other common figures, such as diagonals in rectangles and heights in isosceles and other triangles. The formula for Pythagoras’ theorem is given as c² = a² + b², which could be compared with versions of the formula given in classroom texts. Students could be challenged to express the theorem algebraically for triangles labelled in a different order, or with a different set of letters, or using vertices to names the sides. In preparation for the activities in the Main section, an extra question is given to get students thinking about how Pythagoras’ theorem could be useful. 
Main Activity 
Start the main section of the lesson with the clip Pythagoras’ theorem (2): find the hypotenuse in which Ben tackles an aerial ropeway in order to demonstrate how Pythagoras’ theorem can be applied to the reallife context. He explains how to identify the rightangled triangle and how to use Pythagoras’ theorem to calculate the length of the hypotenuse. It is suggested that the clip is watched in two sections to give an opportunity to review the first part of the calculation and to introduce the use of the square root. Students could find the symbol on their calculators and establish how to use the function. Both sections are supported by accompanying questions, which will enable students to work through Ben’s calculation. They could then generate more examples in the same context. For example, what if the tower was 12 metres high? What if the field was bigger or smaller? The worksheet Pythagoras’ theorem: Practice questions gives students the opportunity to practise this type of calculation:
Students could work through these questions individually before discussing their progress in groups and providing peertopeer feedback. The workings and answers could then be reviewed as a whole class. Worksheet Pythagoras' theorem: Practice questions Worksheet Answers

Plenary 
The plenary is based on the clip Tick or trash: Pythagoras' theorem in which the presenters both tackle a typical exam question involving the use of Pythagoras’ theorem to calculate the length of the hypotenuse. The task is to look carefully at their working out and decide who has the correct answer. Instructions are given for watching this clip in three stages which facilitates an excellent group activity: discuss or attempt the question; vote on whose working to tick and whose to trash; and then discover the correct outcome. The peer assessment approach of this regular feature in Clipbank Maths allows students to review their own understanding and develop their analytical skills. The worksheet Pythagoras’ theorem: Tick or trash is provided as a homework activity. It contains three sets of further ‘Tick or trash’ questions and answers based on using Pythagoras’ theorem to calculate the hypotenuse. These problems highlight a number of typical exam errors and students could write their own revision tips based on their analysis of these questions. Worksheet Pythagoras' theorem: Tick or trash Worksheet Answers

Extension 
Three extension activities are suggested.

Notes on differentiation  The students’ responses to the worksheet tasks will be differentiated by outcome. Using these as group activities facilitates feedback from peers, which can be used to support lower ability pupils.  

Crosscurricular links / Functional skills  English Maths ICT 
Representing, analysing and interpreting. 