reserve a,b,c,d,m,x,n,j,k,l for Nat,
  t,u,v,z for Integer,
  f,F for FinSequence of NAT;
reserve p,q,r,s for real number;

theorem Th67:
  a is odd & 2|^n divides a*b implies 2|^n divides b
  proof
    assume
    A1: a is odd & 2|^n divides a*b; then
    2|^n,a are_coprime by NAT_5:3;
    hence thesis by A1,WSIERP_1:29;
  end;
