 reserve m,n for Nat;
 reserve i,j for Integer;
 reserve S for non empty multMagma;
 reserve r,r1,r2,s,s1,s2,t for Element of S;
 reserve G for Group-like non empty multMagma;
 reserve e,h for Element of G;
 reserve G for Group;
 reserve f,g,h for Element of G;

theorem Th11:
  h * g = 1_G implies h = g" & g = h"
proof
  assume
A1: h * g = 1_G;
  h * h" = 1_G & g" * g = 1_G by Def5;
  hence thesis by A1,Th6;
end;
