public function testProjPerpSumOfSquares(array $A, array $B)
{
$A = new Vector($A);
$B = new Vector($B);
$│A│² = $A->length() ** 2;
$│projᵇA│² = $A->projection($B)->length() ** 2;
$│perpᵇA│² = $A->perp($B)->length() ** 2;
$this->assertEquals($│A│², $│projᵇA│² + $│perpᵇA│²);
}