This type of activity is known as Demonstration. Please read the guidance notes here, where you will find useful information for running these types of activities with your students.

1. Demonstration

• I display the Geogebra page in silence with all information revealed
• I ask students to pause and reflect on what the page shows
• I then hide the area calculation in the second diagram, and move point D up one square
• I ask students to reflect on what has changed and predict what will happen when I reveal the area calculation
• I continue the process, always changing one thing from the original diagram, and always giving students an opportunity to pause, reflect and predict
• At the end I ask students to discuss the rule with their partners, and then we have a class discussion

2. Possible variations

• Vary the height
• Vary the base
• Vary between right-angled and non right-angled triangles
• Vary the top point being “between” the base and to the left-right of the base (i.e. an obtuse angle)

Click here to open sheet full screen in Geogebra