theorem Th62:
  F is having_a_unity & F is associative & F is having_an_inverseOp implies
    (the_inverseOp_wrt F).((the_inverseOp_wrt F).d) = d
proof
  assume
A1: F is having_a_unity & F is associative & F is having_an_inverseOp;
  then F.(d,(the_inverseOp_wrt F).d) = the_unity_wrt F by Th59;
  hence thesis by A1,Th60;
end;
