Directions & Guiding Questions
1. Click on the blue point. Drag the blue point down and watch the triangle get bigger!
Does dragging the blue point to make the triangle bigger, still make this shape a triangle?
2. Click on the pink point. Drag the pink point toward the green point. The triangle gets smaller!
Does dragging the pink point to make the triangle smaller, still make this shape a triangle?
3. Now you have made the shape bigger and smaller, what changes?
What makes a triangle, a triangle? How many sides does a triangle need? How many corners does a triangle need?

Lesson Continued

Once students have manipulated the triangle and identified the attributes that make up a triangle; you can either have them draw or construct (on Geogebra) triangles of their own!