public SidedPlane(Vector p,double x,double y){
  super(x,y);
  sigNum=Math.signum(evaluate(p));
  if (sigNum == 0.0)   throw new IllegalArgumentException("Cannot determine sidedness because check point is on plane.");
}

public SidedPlane ( Vector p , double x , double y ) { super ( x , y ) ; sigNum = Math . signum ( evaluate ( p ) ) ; if ( sigNum == 0.0 ) throw new IllegalArgumentException ( "Cannot determine sidedness because check point is on plane." ) ; }
construct a sided vertical plane from a point and specified x and y coordinates .
