Tetrad (geometry puzzle)

In geometry, a tetrad is four simply connected planar regions in the plane, each pair which share a finite portion of common boundary. It was named by Michael R. W. Buckley in 1975 in the Journal of Recreational Mathematics. A further question was proposed that became a puzzle, whether the 4 regions could be congruent, with or without holes, other enclosed regions.

Tetrad (geometry puzzle)

In geometry, a tetrad is four simply connected planar regions in the plane, each pair which share a finite portion of common boundary. It was named by Michael R. W. Buckley in 1975 in the Journal of Recreational Mathematics. A further question was proposed that became a puzzle, whether the 4 regions could be congruent, with or without holes, other enclosed regions.