theorem Th15:
  for A being Matrix of 0,K holds A={} & A=1.(K,0) & A=0.(K,0)
proof
  let A be Matrix of 0,K;
A1: len A=0 by MATRIX_0:24;
  hence A={};
  hence A=1.(K,0) by Th14;
  thus thesis by A1;
end;
