MathPHP\Probability\Distribution\Continuous\LogLogistic::mean PHP Метод

    public static function mean($α, $β)
    {
        Support::checkLimits(self::LIMITS, ['α' => $α, 'β' => $β]);
        $π = \M_PI;
        if ($β > 1) {
            return $α * $π / $β / sin($π / $β);
        }
        return \NAN;
    }