reserve m,n for Nat;
reserve i,j for Integer;
reserve S for non empty addMagma;
reserve r,r1,r2,s,s1,s2,t,t1,t2 for Element of S;
reserve G for addGroup-like non empty addMagma;
reserve e,h for Element of G;
reserve G for addGroup;
reserve f,g,h for Element of G;
reserve u for UnOp of G;

theorem Th25:
  1 * h = h
proof
  thus 1 * h = ( 0 + 1) * h.= 0 * h+ h by Def7
    .= 0_G + h by Def7
    .= h by Def4;
end;
