Đáp án:
n. \(TXD:D = R\)
Giải thích các bước giải:
\(\begin{array}{l}
DK:{\sin ^2}2x - 1 \ne 0\\
\to \left[ \begin{array}{l}
\sin 2x \ne 1\\
\sin 2x \ne - 1
\end{array} \right.\\
\to \left[ \begin{array}{l}
2x \ne \dfrac{\pi }{2} + k2\pi \\
2x \ne - \dfrac{\pi }{2} + k2\pi
\end{array} \right.\left( {k \in Z} \right)\\
\to \left[ \begin{array}{l}
x \ne \dfrac{\pi }{4} + k\pi \\
x \ne - \dfrac{\pi }{4} + k\pi
\end{array} \right.\left( {k \in Z} \right)\\
\to TXD:D = R\backslash \left\{ {x \ne \dfrac{\pi }{4} + k\pi ;x \ne - \dfrac{\pi }{4} + k\pi } \right\}\\
n.DK:3 - \sin x \ge 0\\
\to 3 \ge \sin x\left( {ld} \right)\\
Do: - 1 \le \sin x \le 1\\
\to TXD:D = R
\end{array}\)
