reserve r for Real;

theorem Th24:
  for x,y,z being Element of 1 holds
  Empty^2-to-zero.(x,z) <= max(Empty^2-to-zero.(x,y),Empty^2-to-zero.(y,z))
proof
  let x,y,z be Element of 1;
A1: z={} by CARD_1:49,TARSKI:def 1;
  x={} & y={} by CARD_1:49,TARSKI:def 1;
  hence thesis by A1;
end;
