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TWO-PAIRS-1

In this movie we simply demonstrate that the four given reflections (in the blue, green, mauve and brown mirror lines) are equivalent to a rotation of 120˚.
(The angle between the first two mirrors and between the second two mirrors is 30˚.)

Before running the movie you might want to examine the reflections more closely and to ask:
• What single transformation maps the grey object flag onto the final image?

Then, after running the movie, it is worth asking students what they think has happened.
• Do they realise the rotation is through 120˚?
• Can they see where the centre of rotation might be?

On the next page, we rotate the first pair of mirror lines and then rotate the second pair, before again rotating the grey flag through 120˚.