Đáp án:
\(\begin{array}{l}
c)TXD:D = R\backslash \left\{ {\dfrac{\pi }{8} + \dfrac{{k\pi }}{2}} \right\}\\
g)TXD:D = R\backslash \left\{ {\dfrac{{2\pi }}{3} + k2\pi } \right\}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
c)DK:\cos \left( {2x + \dfrac{\pi }{4}} \right) \ne 0\\
\to 2x + \dfrac{\pi }{4} \ne \dfrac{\pi }{2} + k\pi \\
\to 2x \ne \dfrac{\pi }{4} + k\pi \\
\to x \ne \dfrac{\pi }{8} + \dfrac{{k\pi }}{2}\left( {k \in Z} \right)\\
\to TXD:D = R\backslash \left\{ {\dfrac{\pi }{8} + \dfrac{{k\pi }}{2}} \right\}\\
g)DK:\cos \left( {\dfrac{x}{2} + \dfrac{\pi }{6}} \right) \ne 0\\
\to \dfrac{x}{2} + \dfrac{\pi }{6} \ne \dfrac{\pi }{2} + k\pi \\
\to \dfrac{x}{2} \ne \dfrac{\pi }{3} + k\pi \\
\to x \ne \dfrac{{2\pi }}{3} + k2\pi \left( {k \in Z} \right)\\
\to TXD:D = R\backslash \left\{ {\dfrac{{2\pi }}{3} + k2\pi } \right\}
\end{array}\)
