reserve x,y,z,r,s for ExtReal;
reserve A,B for ext-real-membered set;

theorem Th38:
  inf {} = +infty
proof
A1: for x being LowerBound of {} holds x <= +infty by XXREAL_0:3;
  +infty is LowerBound of {} by Th36;
  hence thesis by A1,Def4;
end;
