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**Evaluation of some non-elementary integrals involving sine, cosine, exponential and logarithmic integrals. I.**
*(English)*
Zbl 1455.33016

Summary: The non-elementary integrals \(\text{Si}_{\beta,\alpha}=\int [\sin{(\lambda x^\beta)}/(\lambda x^\alpha)] dx, \beta\ge1,\alpha\le\beta+1\) and \(\text{Ci}_{\beta,\alpha}=\int [\cos{(\lambda x^\beta)}/(\lambda x^\alpha)] dx, \beta\ge1,\alpha\le2\beta+1\), where \(\{\beta,\alpha\}\in\mathbb{R} \), are evaluated in terms of the hypergeometric functions \(_1F_2\) and \(_2F_3\), and their asymptotic expressions for \(|x|\gg1\) are also derived. The integrals of the form \(\int [\sin^n{(\lambda x^\beta)}/(\lambda x^\alpha)] dx\) and \(\int [\cos^n{(\lambda x^\beta)}/(\lambda x^\alpha)] dx\), where \(n\) is a positive integer, are expressed in terms \(\text{Si}_{\beta,\alpha}\) and \(\text{Ci}_{\beta,\alpha} \), and then evaluated. \( \text{Si}_{\beta,\alpha}\) and \(\text{Ci}_{\beta,\alpha}\) are also evaluated in terms of the hypergeometric function \(_2F_2\). And so, the hypergeometric functions, \(_1F_2\) and \(_2F_3\), are expressed in terms of \(_2F_2\). The exponential integral \(\text{Ei}_{\beta,\alpha}=\int (e^{\lambda x^\beta}/x^\alpha) dx\) where \(\beta\ge1\) and \(\alpha\le\beta+1\) and the logarithmic integral \(\text{Li}=\int_{\mu}^x dt/\ln{t}, \mu>1\), are also expressed in terms of \(_2F_2\), and their asymptotic expressions are investigated. For instance, it is found that for \(x\gg2, \text{Li}\sim{x}/{\ln{x}}+\ln{\left({\ln{x}}/{\ln{2}}\right)}-2- \ln{2}_2F_2(1,1;2,2;\ln{2})\), where the term \(\ln{\left({\ln{x}}/{\ln{2}}\right)}-2- \ln{2}_2F_2(1,1;2,2;\ln{2})\) is added to the known expression in mathematical literature \(\text{Li}\sim{x}/{\ln{x}} \). The method used in this paper consists of expanding the integrand as a Taylor and integrating the series term by term, and can be used to evaluate the other cases which are not considered here. This work is motivated by the applications of sine, cosine exponential and logarithmic integrals in Science and Engineering, and some applications are given.

For Part II, see [the author, ibid. 4, No. 1, 43–55 (2018; Zbl 1455.33017)].

For Part II, see [the author, ibid. 4, No. 1, 43–55 (2018; Zbl 1455.33017)].

### MSC:

33F05 | Numerical approximation and evaluation of special functions |

33B10 | Exponential and trigonometric functions |

33C05 | Classical hypergeometric functions, \({}_2F_1\) |

41A60 | Asymptotic approximations, asymptotic expansions (steepest descent, etc.) |

### Citations:

Zbl 1455.33017### Software:

DLMF### References:

[1] | Abramowitz M., Stegun I.A., Handbook of mathematical functions with formulas, graphs and mathematical tables, National Bureau of Standards, 1964, 1046 pp. · Zbl 0171.38503 |

[2] | Billingsley P., Probability and measure, 3, John Wiley & Sons Inc., New York, 1995, 608 pp. · Zbl 0822.60002 |

[3] | Hoffman P., The man who loved only numbers, New York Hyperion Books, New York, 1998, 227 pp. · Zbl 0917.01035 |

[4] | Krantz S.G., Handbook of Complex variables, MA Birkhäusser, Boston, 1999, 290 pp. · Zbl 0946.30001 |

[5] | Lebedev N.N., Special functions and their applications, Prentice-Hall Inc., Englewood Cliffs, N.J., 1965 · Zbl 0131.07002 |

[6] | Marchisotto E.A., Zakeri G.-A., “An invitation to integration in finite terms”, College Math. J., 25:4 (1994), 295-308 · Zbl 1291.26013 |

[7] | Nijimbere V., “Evaluation of the non-elementary integral \(\int e^{\lambda x^\alpha} dx, \alpha\ge2\), and other related integrals”, Ural Math. J., 3:2 (2017), 130-142 |

[8] | Nijimbere V., “Evaluation of some non-elementary integrals involving sine, cosine, exponential and logarithmic integrals: Part II”, Ural Math. J., 2018 (to appear) |

[9] | NIST Digital Library of Mathematical Functions |

[10] | Rosenlicht M., “Integration in finite terms”, Amer. Math. Monthly, 79:9 (1972), 963-972 · Zbl 0249.12106 |

[11] | Simon M.K., Alouini M.-S., Digital Communication over Fading Channels, 2, John Wiley & Sons Inc., New York, 2005, 900 pp. |

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