src/Maths/Geometry/Quadrilateral.php
public function isValidPoint(PointInterface $a)
    {
        return (bool) (
            $this->getSegmentAB()->isValidPoint($a) ||
            $this->getSegmentBC()->isValidPoint($a) ||
            $this->getSegmentCD()->isValidPoint($a) ||
            $this->getSegmentDA()->isValidPoint($a)
        );
    }
public function isValidPoint(PointInterface $a)
    {
        return (bool) (
            $this->getSegmentAB()->isValidPoint($a) ||
            $this->getSegmentBC()->isValidPoint($a) ||
            $this->getSegmentCD()->isValidPoint($a) ||
            $this->getSegmentDA()->isValidPoint($a)
        );
    }
Test if point A is part of one of quadrilateral's segments

@param   \Maths\PointInterface   $a
@return  bool