/**
* Subtracts another cartesian vector from this instance
*
* @param static $b
*/
public function subtract(Cartesian $b)
{
$this->x->subtract($b->x);
$this->y->subtract($b->y);
$this->z->subtract($b->z);
if ($this->vx) {
$this->vx->subtract($b->vx);
$this->vy->subtract($b->vy);
$this->vz->subtract($b->vz);
}
return $this;
}
