public function getAbscissaByOrdinate($y)
    {
        $o = $this->getPointO();
        return (sqrt(pow($this->getRadius(), 2) - pow(($y - $o->getOrdinate()), 2)) + $o->getAbscissa());
    }
public function getAbscissaByOrdinate($y)
    {
        $o = $this->getPointO();
        return (sqrt(pow($this->getRadius(), 2) - pow(($y - $o->getOrdinate()), 2)) + $o->getAbscissa());
    }
public function getAbscissaByOrdinate ( $ y ) { $ o = $ this -> getPointO ( ) ; return ( sqrt ( pow ( $ this -> getRadius ( ) , 2 ) - pow ( ( $ y - $ o -> getOrdinate ( ) ) , 2 ) ) + $ o -> getAbscissa ( ) ) ; }
Get the abscissa of a point of the circle by its ordinate

x = sqrt( r^2 - (y - Oy)^2 ) + Ox

@param   float   $y
@return  float
Get the abscissa of a point of the circle by its ordinate