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19 Elliptic IntegralsSymmetric Integrals

§19.20 Special Cases

Contents
  1. §19.20(i) R_{F}\left(x,y,z\right)
  2. §19.20(ii) R_{G}\left(x,y,z\right)
  3. §19.20(iii) R_{J}\left(x,y,z,p\right)
  4. §19.20(iv) R_{D}\left(x,y,z\right)
  5. §19.20(v) R_{-a}\left(\mathbf{b};\mathbf{z}\right)

§19.20(i) R_{F}\left(x,y,z\right)

In this subsection, and also §§19.20(ii)19.20(v), the variables of all R-functions satisfy the constraints specified in §19.16(i) unless other conditions are stated.

The first lemniscate constant is given by

Todd (1975) refers to a proof by T. Schneider that this is a transcendental number. The general lemniscatic case is

19.20.3 R_{F}\left(x,a,y\right)=R_{-\frac{1}{4}}\left(\tfrac{3}{4},\tfrac{1}{2};a^{2},%
xy\right),a=\frac{1}{2}(x+y).

§19.20(ii) R_{G}\left(x,y,z\right)

§19.20(iii) R_{J}\left(x,y,z,p\right)

19.20.7 R_{J}\left(x,y,z,p\right)\to+\infty,p\to 0+ or 0-; x,y,z>0.
19.20.10
\lim_{p\to 0+}\sqrt{p}R_{J}\left(0,y,z,p\right)=\frac{3\pi}{2\sqrt{y}\sqrt{z}},
\lim_{p\to 0-}R_{J}\left(0,y,z,p\right)={-R_{D}\left(0,y,z\right)-R_{D}\left(0%
,z,y\right)}=\frac{-6}{yz}R_{G}\left(0,y,z\right).

where x,y,z may be permuted.

When the variables are real and distinct, the various cases of R_{J}\left(x,y,z,p\right) are called circular (hyperbolic) cases if (p-x)(p-y)(p-z) is positive (negative), because they typically occur in conjunction with inverse circular (hyperbolic) functions. Cases encountered in dynamical problems are usually circular; hyperbolic cases include Cauchy principal values. If x,y,z are permuted so that 0\leq x<y<z, then the Cauchy principal value of R_{J} is given by

valid when

19.20.15
q>0,
p=\frac{z(x+y+q)-xy}{z+q},

or

19.20.16
p=wy+(1-w)z,
w=\frac{z-x}{z+q},
0<w<1.

Since x<y<p<z, p is in a hyperbolic region. In the complete case (x=0) (19.20.14) reduces to

19.20.17 (q+z)R_{J}\left(0,y,z,-q\right)=(p-z)R_{J}\left(0,y,z,p\right)-3R_{F}\left(0,y%
,z\right),p=z(y+q)/(z+q), w=z/(z+q).

§19.20(iv) R_{D}\left(x,y,z\right)

19.20.19 R_{D}\left(x,y,z\right)\sim 3x^{-1/2}y^{-1/2}z^{-1/2},z/\sqrt{xy}\to 0.

The second lemniscate constant is given by

Todd (1975) refers to a proof by T. Schneider that this is a transcendental number. Compare (19.20.2). The general lemniscatic case is

§19.20(v) R_{-a}\left(\mathbf{b};\mathbf{z}\right)

Define c=\sum_{j=1}^{n}b_{j}. Then

where T_{N} is defined by (19.19.1). Also,

19.20.25 R_{-c}\left(\mathbf{b};\mathbf{z}\right)=\prod_{j=1}^{n}z_{j}^{-b_{j}},
19.20.26 R_{-a}\left(\mathbf{b};\mathbf{z}\right)=\prod_{j=1}^{n}z_{j}^{-b_{j}}R_{-a^{%
\prime}}\left(\mathbf{b};\boldsymbol{{z^{-1}}}\right),a+a^{\prime}=c, \boldsymbol{{z^{-1}}}=(z_{1}^{-1},\dots,z_{n}^{-1}).

See also (19.16.11) and (19.16.19).