# Article

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Keywords:
double sine series; sum of a double sine series with monotone coefficients
Summary:
In this paper we obtain estimates of the sum of double sine series near the origin, with monotone coefficients tending to zero. In particular (if the coefficients $a_{k,l}$ satisfy certain conditions) the following order equality is proved $$g(x,y)\sim mna_{m,n}+\frac mn\sum _{l=1}^{n-1}la_{m,l}+\frac nm\sum _{k=1}^{m-1}ka_{k,n}+\frac 1{mn}\sum _{l=1}^{n-1}\sum _{k=1}^{m-1}kla_{k,l},$$ where $x\in (\frac {\pi }{m+1}, \frac {\pi }m]$, $y\in (\frac {\pi }{n+1}, \frac {\pi }n]$, $m, n=1,2,\dots$.
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