theorem Th35:
  a"\/""/\"(X,C) [= "/\"({a"\/"b: b in X}, C)
proof
  set Y = {a"\/"b: b in X};
  Y is_greater_than a"\/""/\"(X,C)
  proof
    let c;
    assume c in Y;
    then consider b such that
A1: c = a"\/"b and
A2: b in X;
    X is_greater_than "/\"(X,C) by Th34;
    then "/\"(X,C) [= b by A2;
    hence thesis by A1,FILTER_0:1;
  end;
  hence thesis by Th34;
end;
