2 câu trả lời
Đáp án:
$$\,D = R\backslash \left\{ {k\pi ;\,\,k \in Z} \right\}$$
Giải thích các bước giải:
$$\eqalign{ & y = {{\cot x} \over {\cos x - 1}} \cr & Ham\,\,so\,\,xac\,\,dinh \cr & \Leftrightarrow \left\{ \matrix{ \sin x \ne 0 \hfill \cr \cos x \ne 1 \hfill \cr} \right. \Leftrightarrow \left\{ \matrix{ x \ne k\pi \hfill \cr x \ne k2\pi \hfill \cr} \right. \Leftrightarrow x \ne k\pi \,\,\left( {k \in Z} \right) \cr & \Rightarrow TXD:\,\,D = R\backslash \left\{ {k\pi ;\,\,k \in Z} \right\} \cr} $$
\[\begin{array}{l} y = \frac{{\cot x}}{{\cos x - 1}}\\ DKXD:\,\,\,\left\{ \begin{array}{l} \sin x \ne 0\\ \cos x - 1 \ne 0 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} \sin x \ne 0\\ \cos x \ne 1 \end{array} \right. \Leftrightarrow \sin x \ne 0 \Leftrightarrow x \ne k\pi \,\,\left( {k \in Z} \right).\\ \Rightarrow D = R\backslash \left\{ {k\pi ,\,\,k \in Z} \right\}. \end{array}\]
