Angela: Wow, girls, this looks amazing! That's a perfect example of reflective symmetry. I'm going to take a photograph of it. A 2D shape is symmetrical if you can draw a line through the middle ...

This means you can draw a mirror line down through the middle of each shape ... to see examples of a mirror line. This pattern is made of squares. The finished pattern has vertical symmetry.

However, I can offer a relatively simple way to draw such a shape using a straight edge and compass. Take an equilateral triangle and extend its sides out across the page. Now, draw an arc centred ...

Ask "What is a triangle?". 2. Using Sketchpad, create a variety of shapes (examples and non-examples of triangles). Begin with open and closed shapes, and shapes with or without straight sides.