Điều kiện:
$\begin{array}{l}
\cos \left( {x + \dfrac{\pi }{3}} \right) \ne 0 \Leftrightarrow x + \dfrac{\pi }{3} \ne \dfrac{\pi }{2} + k\pi \\
\Leftrightarrow x \ne \dfrac{\pi }{6} + k\pi \left( {k \in \mathbb{Z}} \right)
\end{array}$
$\begin{array}{l} {\tan ^2}\left( {x + \dfrac{\pi }{3}} \right) = 1\\ \Leftrightarrow \left[ \begin{array}{l} \tan \left( {x + \dfrac{\pi }{3}} \right) = 1\\ \tan \left( {x + \dfrac{\pi }{3}} \right) = - 1 \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l} x + \dfrac{\pi }{3} = \dfrac{\pi }{4} + k\pi \\ x + \dfrac{\pi }{3} = - \dfrac{\pi }{4} + k\pi \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l} x = - \dfrac{\pi }{{12}} + k\pi \\ x = - \dfrac{{7\pi }}{{12}} + k\pi \end{array} \right.\left( {k \in \mathbb{Z}} \right) \end{array}$
