# Secant

From Encyclopedia of Mathematics

One of the trigonometric functions:

another notation is . Its domain of definition is the whole real line apart from the points

(*) |

The secant is an unbounded even -periodic function. The derivative of the secant is

The indefinite integral of the secant is

The secant can be expanded in a series:

#### Comments

The series expansion is valid in the domain of definition of , i.e. not for the points (*).

#### References

[a1] | K. Knopp, "Theorie und Anwendung der unendlichen Reihen" , Springer (1964) (English translation: Blackie, 1951 & Dover, reprint, 1990) |

[a2] | M. Abramowitz, I.A. Stegun, "Handbook of mathematical functions" , Dover, reprint (1965) pp. §4.3 |

**How to Cite This Entry:**

Secant.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Secant&oldid=13004

This article was adapted from an original article by Yu.A. Gor'kov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article