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Note your browser must be set up for Java applets. Each page uses the Cinderella java applet, so allow time for the page to fully download. Each page contains interactive geometry that can be controlled by "click and drag" movements of the mousepointer. Buttons may be available on the left of screen to permit more interactivity.
Find more information on interactive geometry at MathsNet.
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1. Rotational symmetry
Introducing the idea of rotation and possibly - the order of rotational symmetry or the angles turned through to match up the vertices.
2. Rotational symmetry
A rotation of 180 degrees. Can you make the blue shape cover the yellow shape?
3. Angles of rotation
Quarter turns (90 degrees), half turns (180 degrees), three-quarter turns (270 degrees) and full turns (360 degrees). Pick an angle of rotation and estimate where the blue triangle should be positioned.
4. Angles of rotation
Angles measured in degrees anticlockwise. Move the "angle of rotation = ..." display to the right so the angle itself is off-screen and get pupils to estimate angles.
5. Rotation puzzle
Find the angle that makes a regular hexagon. [Answer = 60 degrees.]
6. Rotation jigsaw
Find the angle and centre that fits the yellow triangle into the gap.
[Answer: centre at (5,0), angle about 125-6 degrees]
7. Rotation jigsaw
Find the angle and centre that fits the purple triangle into the gap.
[Answer: centre at (5,0), angle about 121-2 degrees]
8. Rotation puzzle
Find the angle and centre that rotates the yellow to the purple quadrilateral.
[Answer: centre at (3.7, 8.2), angle about 212 degrees]
9. Rotation construction
Construct the centre of the rotation.
10. Rotation construction
Construct the centre of the rotation.