public static function CDF($x, $α, $β) { Support::checkLimits(self::LIMITS, ['x' => $x, 'α' => $α, 'β' => $β]); $⟮x/α⟯⁻ᵝ = pow($x / $α, -$β); return 1 / (1 + $⟮x/α⟯⁻ᵝ); }