Công thức nào sau đây đúng?

\(\sin x = \sin \alpha \Leftrightarrow \left[ \begin{array}{l}x = \alpha + k2\pi \\x = \pi - \alpha + k2\pi \end{array} \right.,\,k \in \mathbb{Z}\).

\(\tan x = \tan \alpha \Leftrightarrow x = \alpha + k2\pi ,\,k \in \mathbb{Z}\).

\(\tan x = \tan \alpha \Leftrightarrow x = 2\alpha + k\pi ,\,k \in \mathbb{Z}\).

\(\cos x = \cos \alpha \Leftrightarrow \left[ \begin{array}{l}x = \alpha + k2\pi \\x = \pi - \alpha + k2\pi \end{array} \right.,\,k \in \mathbb{Z}\).