protected static Dfp atanInternal(final Dfp a){
  Dfp y=new Dfp(a);
  Dfp x=new Dfp(y);
  Dfp py=new Dfp(y);
  for (int i=3; i < 90; i+=2) {
    x=x.multiply(a);
    x=x.multiply(a);
    x=x.negate();
    y=y.add(x.divide(i));
    if (y.equals(py)) {
      break;
    }
    py=new Dfp(y);
  }
  return y;
}

protected static Dfp atanInternal ( final Dfp a ) { Dfp y = new Dfp ( a ) ; Dfp x = new Dfp ( y ) ; Dfp py = new Dfp ( y ) ; for ( int i = 3 ; i < 90 ; i += 2 ) { x = x . multiply ( a ) ; x = x . multiply ( a ) ; x = x . negate ( ) ; y = y . add ( x . divide ( i ) ) ; if ( y . equals ( py ) ) { break ; } py = new Dfp ( y ) ; } return y ; }
computes the arc - tangent of the argument .
