Secant

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