Author: Jackie Juden

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 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
• 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 y-intercept – how many intersections are there?
• Vary the gradient of 1 line – must they cross?
• Which has the larger gradient?
• Vary the gradient until they are perpendicular What is true?
• Is the gradient always positive?
• Is the gradient always an integer?
• Explain the gradient when y = 1 or y = -1

Click here to open sheet full screen in Geogebra