src/Maths/Geometry/Disc.php
public function isValidPoint(PointInterface $a)
    {
        $s = new Segment($this->getPointO(), $a);
        return (bool) ($s->getLength() <= $this->getRadius());
    }
public function isValidPoint(PointInterface $a)
    {
        $s = new Segment($this->getPointO(), $a);
        return (bool) ($s->getLength() <= $this->getRadius());
    }
Test if a point is part of the disc ([O->a] <= r)

@param   \Maths\PointInterface   $a
@return  bool