GCSE Lesson introducing Pythagoras - planned for Top Set Year 9. Start with Tarsia puzzle on squares/square roots. Then investigative worksheet (only item not included here as made offline) of triangles of different sizes - ask students to measure each triangle and complete a table with the headings 'a', &'a squared&';, 'b&', &';b squared', &'c&';, 'c squared&' - see if they can spot a relationship. Then examples and questions set in Powerpoint, followed by differentiated worksheet. Plenary: WILT activity.