(1-1+1-1+...) ²=1-2+3-4+...
#series

Image from "On Spherical Drawing and Computation" by Milton Felstein. American Mathematical Monthly. November, 1955.

An open knight's tour of a 64x64 chessboard. The knight starts in the lower left corner, finishes near the lower right corner, and visits each of the 8x8 squares (that look like a U or a rotated U) in the same order that they'd be visited by a third-stage Hilbert curve.

#phi #goldenratio

#circle #pi

#topology #humor

a³-b³=(a-b) (a²+ab+b²)
#geometry

Klein bottle #topology

Japanese theorem:
no matter how one triangulates a cyclic polygon, the sum of inradii of triangles is constant.

The Cistercian monks invented a numbering system in the 13th century which meant that any number from 1 to 9999 could be written using a single symbol.
#history

#latex basics

Surface area of sphere
#geometry #integrals

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