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**Opalg** The function F is monotonic in each of the intervals $\displaystyle \left[\frac1{\bigl(n+\tfrac12\bigr)\pi}, \frac1{\bigl(n-\tfrac12\bigr)\pi}\right]$, in which the variation is less than $\displaystyle \frac{2}{\bigl(n-\tfrac12\bigr)^2\pi^2}$.

The function G is monotonic in each of the intervals $\displaystyle \left[\frac1{\sqrt{\bigl(n+\tfrac12\bigr)\pi}}, \frac1{\sqrt{\bigl(n-\tfrac12\bigr)\pi}}\right]$, in which the variation is greater than $\displaystyle \frac{2}{\bigl(n+\tfrac12\bigr)\pi}$.