2 câu trả lời
Đáp án:
Giải thích các bước giải:
ĐKXĐ: $$\eqalign{ & \left\{ \matrix{ \cos x \ne 0 \hfill \cr \tan 3x \ne - 1 \hfill \cr} \right. \Leftrightarrow \left\{ \matrix{ x \ne {\pi \over 2} + k\pi \hfill \cr 3x \ne - {\pi \over 4} + k\pi \hfill \cr} \right. \Leftrightarrow \left\{ \matrix{ x \ne {\pi \over 2} + k\pi \hfill \cr x \ne - {\pi \over {12}} + {{k\pi } \over 3} \hfill \cr} \right.\left( {k \in Z} \right) \cr & \Rightarrow D = R\backslash \left\{ {{\pi \over 2} + k\pi ; - {\pi \over {12}} + {{k\pi } \over 3},k \in Z} \right\} \cr} $$
Đáp án:
Giải thích các bước giải: \((\begin{array}{*{20}{l}}{y = tanx/tan3x + 1}\\{y = \frac{{\tan {\mkern 1mu} x}}{{\tan {\mkern 1mu} 3x + 1}}}\\{DK:{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} \left\{ {\begin{array}{*{20}{l}}{cosx \ne 0}\\{cos3x \ne 0}\\{\tan 3x \ne - 1}\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}{l}}{x \ne \frac{\pi }{2} + k\pi }\\{x \ne \frac{\pi }{6} + k\pi }\\{x \ne \frac{{ - \pi }}{{12}} + \frac{{k\pi }}{3}}\end{array}} \right.{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} \left( {k \in Z} \right)}\end{array}\)
