https://en.wikipedia.org/wiki/Duality_(mathematics)
https://en.wikipedia.org/wiki/Involution_(mathematics)
This is a special case of BP841 and a generalisation of BP822.
Adjacent-numbered pages: BP1105 BP1106 BP1107 BP1108 BP1109  *  BP1111 BP1112 BP1113 BP1114 BP1115
nice, abstract, math, anticomputer, creativeexamples, left-narrow, unorderedpair, rules, miniworlds, dithering
Leo Crabbe