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22 Jacobian Elliptic FunctionsProperties

§22.16 Related Functions

Contents
  1. §22.16(i) Jacobi’s Amplitude () Function
  2. §22.16(ii) Jacobi’s Epsilon Function
  3. §22.16(iii) Jacobi’s Zeta Function
  4. §22.16(iv) Graphs

§22.16(i) Jacobi’s Amplitude () Function

Definition

22.16.1
,

where the inverse sine has its principal value when and is defined by continuity elsewhere. See Figure 22.16.1. is an infinitely differentiable function of .

Quasi-Periodicity

Integral Representation

Special Values

22.16.4
22.16.5

For the Gudermannian function see §4.23(viii).

Approximation for Small

Approximations for Small ,

Fourier Series

Relation to Elliptic Integrals

If , then the following four equations are equivalent:

22.16.10
22.16.11
22.16.12
22.16.13

For see §19.2(ii).

§22.16(ii) Jacobi’s Epsilon Function

Integral Representations

For ,

22.16.14

compare (19.2.5). See Figure 22.16.2.

Quasi-Addition and Quasi-Periodic Formulas

Relation to Theta Functions

Relation to the Elliptic Integral

§22.16(iii) Jacobi’s Zeta Function

Definition

With and as in §19.2(ii) and ,

22.16.32

See Figure 22.16.3. (Sometimes in the literature is denoted by .)

Properties

§22.16(iv) Graphs

See accompanying text
Figure 22.16.1: Jacobi’s amplitude function for and . Values of greater than 1 are illustrated in Figure 22.19.1. Magnify
See accompanying text
Figure 22.16.2: Jacobi’s epsilon function for and . (These graphs are similar to those in Figure 22.16.1; compare (22.16.3), (22.16.17), and the graphs of in §22.3(i).) Magnify
See accompanying text
Figure 22.16.3: Jacobi’s zeta function for and . Magnify
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