English

Evaluation of some non-elementary integrals involving sine, cosine, exponential and logarithmic integrals: Part I

Classical Analysis and ODEs 2018-08-02 v2

Abstract

The non-elementary integrals Siβ,α=[sin(λxβ)/(λxα)]dx,β1,αβ+1\text{Si}_{\beta,\alpha}=\int [\sin{(\lambda x^\beta)}/(\lambda x^\alpha)] dx,\beta\ge1,\alpha\le\beta+1 and Ciβ,α=[cos(λxβ)/(λxα)]dx,β1,α2β+1\text{Ci}_{\beta,\alpha}=\int [\cos{(\lambda x^\beta)}/(\lambda x^\alpha)] dx, \beta\ge1, \alpha\le2\beta+1, where {β,α}R\{\beta,\alpha\}\in\mathbb{R}, are evaluated in terms of the hypergeometric functions 1F2_{1}F_2 and 2F3_{2}F_3, and their asymptotic expressions for x1|x|\gg1 are also derived. The integrals of the form [sinn(λxβ)/(λxα)]dx\int [\sin^n{(\lambda x^\beta)}/(\lambda x^\alpha)] dx and [cosn(λxβ)/(λxα)]dx\int [\cos^n{(\lambda x^\beta)}/(\lambda x^\alpha)] dx, where nn is a positive integer, are expressed in terms Siβ,α\text{Si}_{\beta,\alpha} and Ciβ,α\text{Ci}_{\beta,\alpha}, and then evaluated. Siβ,α\text{Si}_{\beta,\alpha} and Ciβ,α\text{Ci}_{\beta,\alpha} are also evaluated in terms of the hypergeometric function 2F2_{2}F_2. And so, the hypergeometric functions, 1F2_{1}F_2 and 2F3_{2}F_3, are expressed in terms of 2F2_{2}F_2.The exponential integral Eiβ,α=(eλxβ/xα)dx\text{Ei}_{\beta,\alpha}=\int (e^{\lambda x^\beta}/x^\alpha) dx where β1\beta\ge1 and αβ+1\alpha\le\beta+1 and the logarithmic integral Li=μxdt/lnt,μ>1\text{Li}=\int_{\mu}^{x} dt/\ln{t}, \mu>1 are also expressed in terms of 2F2_{2}F_2, and their asymptotic expressions are investigated. It is found that for xμx\gg\mu, Lix/lnx+ln(lnxlnμ)2lnμ2F2(1,1;2,2;lnμ)\text{Li}\sim {x}/{\ln{x}}+\ln{\left(\frac{\ln{x}}{\ln{\mu}}\right)}-2-\ln{\mu}\hspace{.075cm} _{2}F_{2}(1,1;2,2;\ln{\mu}), where the term ln(lnxlnμ)2lnμ2F2(1,1;2,2;lnμ)\ln{\left(\frac{\ln{x}}{\ln{\mu}}\right)}-2-\ln{\mu}\hspace{.075cm} _{2}F_{2}(1,1;2,2;\ln{\mu}) is added to the known expression in mathematical literature Lix/lnx\text{Li}\sim {x}/{\ln{x}}.

Keywords

Cite

@article{arxiv.1703.01907,
  title  = {Evaluation of some non-elementary integrals involving sine, cosine, exponential and logarithmic integrals: Part I},
  author = {Victor Nijimbere},
  journal= {arXiv preprint arXiv:1703.01907},
  year   = {2018}
}

Comments

23 pages, 1 figure, Accepted for publication by the Ural Math. J