Đáp án:
\(D = \mathbb{R}\backslash \left\{ {\dfrac{{k\pi }}{2},k \in \mathbb{Z}} \right\}\)
Giải thích các bước giải:
ĐK:
\(\begin{array}{l}\left\{ \begin{array}{l}\cos x \ne 0\\\tan x - \sin x \ne 0\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}\cos x \ne 0\\\sin x\left( {\dfrac{1}{{\cos x}} - 1} \right) \ne 0\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}\cos x \ne 0\\\sin x \ne 0\\\cos x \ne 1\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}\cos x \ne 0\\\sin x \ne 0\end{array} \right.\\ \Leftrightarrow \sin 2x \ne 0 \Leftrightarrow 2x \ne k\pi \Leftrightarrow x \ne \dfrac{{k\pi }}{2},k \in \mathbb{Z}\end{array}\)
Vậy TXĐ: \(D = \mathbb{R}\backslash \left\{ {\dfrac{{k\pi }}{2},k \in \mathbb{Z}} \right\}\)
