theorem Th61:
  width <*pf*> = len pf
  proof
A1: len <*pf*> = 1 by FINSEQ_1:39;
    rng <*pf*> = {pf} by FINSEQ_1:39;
    then pf in rng <*pf*> by TARSKI:def 1;
    hence thesis by A1,MATRIX_0:def 3;
end;
