(*$B- Aufgabe 2.14*)
PROGRAM berechnungvonpi;
VAR x, pi:real;

FUNCTION atan(x:real):real;
VAR s,salt, t : real; i: integer;
BEGIN
  s :=x; t :=x ; i := 1;
  REPEAT
     salt :=s; i:= i+2 ; t := -t*x*x; s:=salt+t/i
  UNTIL s = salt;
  atan := s
END;

BEGIN
  pi := 24*atan(1/8)+8*atan(1/57)+4*atan(1/239);
  writeln(pi,'  exakter Wert =', 4*arctan(1))
END.