* Bill Gosper <billgosper@gmail.com> [Nov 08. 2019 15:44]:
[...]] Kids: I somehow missed (or completely forgot) the cool integral for the area of the curve enclosed by {x(t),y(t)}: ½∲(x dy - y dx).
And for the discrete kids, one also has to mention https://en.wikipedia.org/wiki/Shoelace_formula With this one and an automaton for the border of the twin-dragon ( see Example 4.4 in F.\ M.\ Dekking: {Recurrent Sets}, Advances in Mathematics, vol.~44, no.~1, pp.~78-104, (1982). http://dx.doi.org/10.1016/0001-8708(82)90066-4 (now open access) ) you should be able to compute good approximations of the area of the twin-dragon (you asked about it in another email, I seem to recall). Best regards, jj P.S.: Should I feel stupid because I cannot grasp the commutative diagram on page 79? (I really tried!)
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