set A = bool the carrier of R;
set B = [#] R;
set ff = SymmetricDiffDist ([#] R);
set p = {} ([#] R);
JaccardDist ([#] R) = SteinhausGen ((SymmetricDiffDist ([#] R)),({} ([#] R))) by LastLemma;
hence MarczewskiDistance R is triangle ; :: thesis: verum