(* Algorithmus 2.10 *)
PROCEDURE csqrt(a:komplex; VAR w:komplex);
VAR r,phi : real;
BEGIN
  topolar(a.re,a.im,r,phi);
  r:=sqrt(r); phi:=phi/2;
  w.re:=r*cos(phi); w.im:=r*sin(phi)
END;