\textbf{189-} The equation of lateral energy -- time of a simple harmonic oscillator with mass $100$ g in SI is $K = 45\pi^2 \times 10^{-4}\cos^2(10\pi t)$. How many centimeters is the displacement of the oscillator in the time interval from $t_1 = \dfrac{1}{20}$ s to $t_2 = \dfrac{3}{20}$ s?
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(1) zero \hfill (2) $2$ \hfill (3) $3$ \hfill (4) $6$
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