Left: The large rectangle is plastic and can be split into a square (blue) and two plastic rectangles (red and {green).
Centre: The two arcs drawn in each square.
Right: A Harriss spiral.
Image: Chalkdust.
More from Chalkdust
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Dispersion on the dark side of the moon
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Carnival of Mathematics 133
This month's round up of mathematical blog posts.
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In conversation with Hannah Fry
On the mathematics of love, communicating maths to the public, and women in maths.