reserve i,j,n for Nat,
  K for Field,
  a for Element of K,
  M,M1,M2,M3,M4 for Matrix of n,K;
reserve A for Matrix of K;

theorem
  for R being Ring
  holds ((1.(R,n))~)~ = 1.(R,n)
proof
  let R be Ring;
  (1.(R,n))~ = 1.(R,n) by Th9;
  hence thesis;
end;
