My son told me he can make a sphere from three circles. How would you make a sphere from three circles?
@peterrowlett If you draw three mutually perpendicular circles, with the same radius and center, it looks a lot like a sphere. Especially if you then shade the sphere itself. Here's an example, using the Borromean rings: (the triples of circles have been projected onto the plane, becoming aspect-ratio-2 ellipses):
Saw this in a comic book in the 70s... Draw three circles on paper, cut them out. Fold in half to cut like so: in one you cut a central cross, size one radius. In another, cut a central slot, length one radius. In the third, cut two half-radius slots from opposite sides, the complement of the central cross. Now, by folding from the edge to the centre, insert the third into the second, then insert those two into the first.
Three perpendicular circles - a sphere.
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