$\begin{array}{l}
\sqrt {4 - {x^2}} \sin 2x = 0\,\,\,\left( * \right)\\
DK:\,\,\,4 - {x^2} \ge 0 \Leftrightarrow - 2 \le x \le 2\\
\left( * \right) \Leftrightarrow \left[ \begin{array}{l}
\sqrt {4 - {x^2}} = 0\\
\sin 2x = 0
\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}
{x^2} - 4 = 0\\
2x = k\pi \,\,\,
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = \pm 2\\
x = \frac{{k\pi }}{2}\,\,\left( {k \in Z} \right)
\end{array} \right.\\
- 2 \le x \le 2 \Rightarrow - 2 \le \frac{{k\pi }}{2} \le 2 \Leftrightarrow - 1,27 \le k \le 1,27\\
\Rightarrow k = 0 \Rightarrow x = 0\\
Vay\,\,pt\,\,co\,\,tap\,\,nghiem:\,\,\,S = \left\{ { - 2;\,\,0;\,\,2} \right\}.
\end{array}$
