Author: Jess Prior

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, ensuring the two images are identical
• I ask students to pause and reflect on what the page shows
• I then hide one of the angles in the second diagram, and move one of the points on the circumference
• I ask students to reflect on what has changed and predict what will happen when I reveal the size of the angle
• The consider this first on their own, and then discuss it with a neighbour
• I then reveal the size of the missing angle
• 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
• Please read the guidance notes here for more information about running these types of Demonstrations.

2. Possible variations

• Vary the size of one angle
• Vary the length of the line segment
• Vary the orientation of the “base” line
• Vary the angle that is hidden

Click here to open sheet full screen in Geogebra