Angles in Triangles add to 180 degrees

This app allows you to explore the reasons why angles within a triangle add up to 180 degrees. By cutting the corners off of a triangle and seeing what shape they make as well as looking at alternate angles you should be able to see some relationships forming. Here are some instructions on how to use the app: The 2 lines are PARALLEL, there are 2 triangles hidden 1. ‘Alternate angle triangle’ and 2. ‘Triangle to split’. Tick the box to reveal the triangles and move the sliders under the tick boxes to see what happens. (NOTE: only have one triangle ticked at any one time). You can also move the ‘rotate triangle and parallel lines’ slider or the ‘change triangle shape’ slider at any time. Have fun and hope you learn something