Litipk\BigNumbers\Decimal::tan PHP 메소드

    public function tan($scale = null)
    {
        $cos = $this->cos($scale + 2);
        if ($cos->isZero()) {
            throw new \DomainException("The tangent of this 'angle' is undefined.");
        }
        return $this->sin($scale + 2)->div($cos)->round($scale);
    }