public function testProjPerpPerpDotProductEqualsProductOfLengths(array $A, array $B)
{
$A = new Vector($A);
$B = new Vector($B);
$projᵇA = $A->projection($B);
$projᵇA⊥ = $A->projection($B)->perpendicular();
$perpᵇA = $A->perp($B);
$projᵇA⊥⋅perpᵇA = abs($projᵇA⊥->dotProduct($perpᵇA));
$│projᵇA│ = $projᵇA->length();
$│perpᵇA│ = $perpᵇA->length();
$this->assertEquals($projᵇA⊥⋅perpᵇA, $│projᵇA│ * $│perpᵇA│);
}