theorem
  for s being Real holds Rotate(s) = Rotate(s+2*PI*i)
  proof
    let s be Real;
    let p be Point of T2;
    set q = p`1+(p`2)*<i>;
A1: Rotate(q,s) = Rotate(q,s+2*PI*i) by Th39;
    thus (Rotate(s)).p = |[Re Rotate(q,s),Im Rotate(q,s)]| by JORDAN24:def 3
    .= (Rotate(s+2*PI*i)).p by A1,JORDAN24:def 3;
  end;
