123. The area bounded by the curve $y = \sqrt{1 - \cos 2x}$ and the $x$-axis over one period is: (1) $2$ (2) $2\sqrt{2}$ (3) $3$ (4) $3\sqrt{2}$
\textbf{123.} The area bounded by the curve $y = \sqrt{1 - \cos 2x}$ and the $x$-axis over one period is:
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(1) $2$ \hfill (2) $2\sqrt{2}$ \hfill (3) $3$ \hfill (4) $3\sqrt{2}$
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