English

Cancellations in power series of sine type

Classical Analysis and ODEs 2015-05-05 v1

Abstract

We present a method to study the behavior of a power series of type f(x):=n=0(1)ncnx2n+1(2n+1)!f(x):=\sum_{n=0}^\infty (-1)^n c_n\frac{x^{2n+1}}{(2n+1)!} when xx\to\infty. We apply our method to study the function f(t):=0tdxx0xdyy0ydzz{sinx+sin(xy)sin(xz)sin(xy+z)}.f(t):=\int_0^t\frac{dx}{x}\int_0^x\frac{dy}{y}\int_0^y\frac{dz}{z}\bigl\{ \sin x+\sin(x-y)-\sin(x-z)-\sin(x-y+z)\bigr\}. We will derive various different representations of f(t)f(t) by means of which it will be shown that limt+f(t)=0\lim_{t\to+\infty}f(t)=0, disproving a conjecture by Z. Silagadze, claiming that this limit equals π3/12-\pi^3/12.

Keywords

Cite

@article{arxiv.1505.00440,
  title  = {Cancellations in power series of sine type},
  author = {Juan Arias de Reyna},
  journal= {arXiv preprint arXiv:1505.00440},
  year   = {2015}
}

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12 pages