
theorem
  for a,b be Complex, n,k be Nat st k in Seg(n+1)
    ex c be object, l,m be Nat st m = k-1 & l = n-m & c = a|^l*b|^m
    proof
      let a,b be Complex, n,k be Nat such that
      B1: k in Seg (n+1);
      consider m1,l1 be Nat such that
      B2: m1 = k - 1 & l1 = n - m1 by B1,LmN;
      a|^l1*b|^m1 is object;
      hence thesis by B2;
    end;
