The cosine function, $\cos(x)$, has a fundamental period of $2\pi$. This means that $\cos(x) = \cos(x + 2\pi)$. For a function of the form $\cos(kx)$, the period changes to $\frac{2\pi}{k}$. Therefore, the functions $\cos \frac{p}{q} t$ and $\cos \frac{r}{s} t$
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