echo date("Y-m-d H:i:s") . "\n";
echo "==\nVector v1: " . $v1->toString() . "\n";
echo "Vector v2: " . $v2->toString() . "\n";
$r = Math_VectorOp::add($v1, $v2);
echo "v1 + v2: " . $r->toString() . "\n";
$r = Math_VectorOp::substract($v1, $v2);
echo "v1 - v2: " . $r->toString() . "\n";
$r = Math_VectorOp::multiply($v1, $v2);
echo "v1 * v2: " . $r->toString() . "\n";
$r = Math_VectorOp::divide($v1, $v2);
echo "v1 / v2: " . $r->toString() . "\n";
echo "==\nVector w1: " . $w1->toString() . "\n";
echo "Vector w2: " . $w2->toString() . "\n";
echo "Vector w3: " . $w3->toString() . "\n";
$r = Math_VectorOp::scale(2.0, $w1);
echo " 2.0 * w1 = " . $r->toString() . "\n";
$r = Math_VectorOp::dotProduct($w1, $w2);
echo "w1 . w2 = {$r}\n";
$r = Math_VectorOp::crossProduct($w2, $w3);
echo "w2 x w3 = " . $r->toString() . "\n";
echo "The triple scalar product of 3 vectors is the volume\r\nof the parallelepiped defined by the vectors. Three coplanar\r\nvectors must give a volume of zero, w1, w2 and w3 are coplanar\n";
$r = Math_VectorOp::tripleScalarProduct($w1, $w2, $w3);
echo "w1 . (w2 x w3) = {$r}\n";
$z = Math_VectorOp::createOne(3);
echo "Now we introduce z : " . $z->toString() . "\n";
echo "and z not being coplanar to w1, w2, or w3:\n";
$r = Math_VectorOp::tripleScalarProduct($z, $w2, $w3);
echo "z * (w2 x w3) = {$r}\n";
$r = Math_VectorOp::angleBetween($z, $w1);
echo "and the angle between z and w1 is {$r} radians\n";
echo "which is " . $r * 180.0 / M_PI . " degrees\n";
