reserve x,y,y1,y2 for set;
reserve C for non empty set;
reserve c for Element of C;
reserve f,h,g,h1 for Membership_Func of C;

theorem
  1_minus (f\g) = max(1_minus f,g)
proof
  thus 1_minus (f\g) = max(1_minus f,1_minus(1_minus g)) by FUZZY_1:11
    .= max(1_minus f,g);
end;
