Mathfilter: In Gelfand's exceptional Algebra text, he is talking about the formula 1 + x + x^2 + x^3 + ... = 1/(1 - x). He uses the Achilles racing the tortoise model when first introducing the formula. He discusses the case x = 10, whence 1 + 10 + 100 + 1000 + ... = -1/9. [more inside]
posted by wittgenstein
on Jul 27, 2011 -
What do you call those three-dimensional geometric novelties, consisting of eight cubes, joined to each other at one edge to form one large cube, whose pieces can be flipped around to display different images on the exterior of the large cube? What is the history of this delightful object? What are the geometric priniciples behind it?
posted by Faze
on Jan 20, 2005 -
About a year ago, someone posted a wonderful link over in the blue that detailed a certain aspect in the design of paper currency, stock certificates, and the like... it had a specific name, but I can't recall what it is — so I can't google for the Mefi thread.
What do you call the geometric drawing comprised of very fine lines and lots of repetition — they look a lot like spiralgraph output — that adorns paper currency, stock certificates, and the like?
posted by silusGROK
on Dec 8, 2004 -