Sine Integral and Cosine Integral

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Sine Integral and Cosine Integral

 

special functions respectively defined by the integrals

These functions were introduced by the Italian mathematician L. Mascheroni in 1790. However it was already known (1781) to L. Euler that

This integral is the simplest example of an improper integral that is convergent but not absolutely convergent. The functions Si (x) and Ci (x) are encountered in various problems of analysis and engineering, and comprehensive tables of them are available.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.