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Analytical solutions of incomplete elliptic integrals motivated by the

work of Ramanujan

M. I. Qureshi

a

, C. W. Mohd

b

, M. P. Chaudhary

c,∗

, K. A. Quraishi

d

and I. H. Khan

d

a,bDepartment of Applied Sciences and Humanities, Faculty of Engineering and Technology, Jamia Millia Islamia, New Delhi-110025, India.

c,dFormer Researcher, Department of Applied Sciences and Humanities, Faculty of Engineering and Technology, Jamia Millia Islamia, New Delhi-110025, India.

Abstract

In this paper, we obtain exact solutions of some unsolved incomplete elliptic integrals of first, second and

third kinds, given in Entry 7 of Chapter XVII of second notebook of Srinivasa Ramanujan. Furthermore,

we generalize these elliptic integrals in the forms of multiple series identities involving bounded multiple

sequences.

Keywords: Gaussian Hypergeometric Function; Incomplete Elliptic Integrals; Multiple Series Identities;

Srivastava-Daoust double Hypergeometric Function ; Kamp´e de F´eriet double Hypergeometric Function;

Sri-vastava’s Triple Hypergeometric Function.

2010 MSC:33B10, 33C05,, 33C65. 2012 MJM. All rights reserved.c

1

Introduction and Preliminaries

Some Interesting Series Identities

We recall the following identities which are potentially useful in the series rearrangement techniques.

m=0 m−1

r=0

Θ(m, r) =

m=0

r=0

Θ(m+r+1, r) (1.1)

m=0 2m−1

r=0

Θ(m, r) =

m=0

r=0

Θ(m+r+1, r) +

m=0

r=0

Θ(m+r+1, 2r+m+1) (1.2)

Corresponding author.

E-mail address:miqureshi [email protected](M. I. Qureshi),mpchaudhary [email protected](M. P. Chaudhary),[email protected]

(2)

m=0

n=0 m+n−1

r=0

Ψ(m, n, r) =

n=0

r=0

Ψ(0, n+r+1, r) +

m=0

n=0

r=0

Ψ(m+r+1, n, r)+

+

m=0

n=0

r=0

Ψ(m+1, n+r+1, r+m+1) (1.3)

m=0

n=0 m+n

r=0

Ψ(m, n, r) =

m=0

n=0

r=0

Ψ(m+r, n, r) +

m=0

n=0

r=0

Ψ(m, n+r+1, r+m+1) (1.4)

where{Θ(m,r)}∞m,r=0and{Ψ(m,n,r)}∞m,n,r=0are suitably bounded double and triple sequences of essentially arbitrary(real or complex) parameters respectively.

Legendre’s Normal Forms of Incomplete Elliptic Integrals

Following integrals arise in the solutions of certain classes of vibration problems and problems involving

computations of the radiation field off axis from a uniform circular disc radiating according to an arbitrary

angular distribution law.

Following elliptic integrals (R.H.S.) have been represented in different notations (L.H.S.) by researchers

First Kind : F(x, φ) =

Z φ

0

dθ

q

(1−x2sin2 θ)

(1.5)

Second Kind : E(x, φ) =

Z φ

0

q

(1−x2sin2

θ)dθ (1.6)

Third Kind :

(a, x, φ) =

Z φ

0

dθ

(1−asin2θ)

q

(1−x2sin2θ)

(1.7)

where 0≤ x≤ 1, 0≤ φπ

2, −∞<a<∞, a6=1

The integrands of elliptic integrals are periodic functions with a periodπ. Herex, φandaare called modulus,

amplitude and characteristic parameter respectively. In casex=sinδ,δis called modular angle.

Some Useful Indefinite Integrals

Whenm=0, 1, 2, 3,· · ·, then

Z

sin2m(cθ)dθ=

(

−(12)msin(cθ)cos(cθ) (1)m c

m−1

r=0

(1)rsin2r(cθ) (32)r

)

+

(

θ(12)m

(1)m

)

+Constant (1.8)

Z

cos2m(cθ)dθ=

(

(12)msin(cθ)cos(cθ) (1)m c

m−1

r=0

(1)rcos2r(cθ) (32)r

)

+

(

θ(12)m

(1)m

)

+Constant (1.9)

Z

sin2m+1(cθ)dθ= −(1)mcos(cθ)

(32)m c m

r=0

(12)rsin2r(cθ)

(1)r

+Constant (1.10)

Z

cos2m+1(cθ)dθ= (1)msin(cθ)

(32)m c m

r=0

(12)rcos2r(cθ)

(1)r +Constant (1.11)

Above formulas (1.8)-(1.11) can be verified form=0, 1, 2, 3,· · · and it is the convention that the empty sum −1

r=0

(3)

2

Seventh entry of Chapter Seventeenth of Second Notebook of

Ramanujan[9,pp.104-107,pp.112-113]

Ramanujan’s notebooks have been divided into several chapters and contains large numbers of important

and useful results on elliptic integrals. Many results on elliptic integrals have been proved by B. C. Berndt [8,

pp.104-113] and R. Y. Deniset al.[15].

We have also verified the following entries of Ramanujan by using the methods of B. C. Berndt and R. Y. Denis

et al.

Entry 7(i): If sinα= √

xsinβortantanαβ =

xcosβ

(1−xsin2β), then Z α

0

dθ

q

(x−sin2θ)

=

Z β

0

dθ

q

(1−xsin2θ)

(2.1)

In a paper of Deniset al.[15, p.113(1)], a misprint condition is written in Entry 7(i).

Entry 7(ii): If tanα=p(1−x)tanβor sinα= √

(1−x)sinβ

(1−xsin2β), then

Z α

0

dθ

p

(1−xcos2θ) =

Z β

0

dθ

q

(1−xsin2θ)

(2.2)

Entry 7(iii): If tanα=p(1−b)tanβor sinβ= √ sinα

(1−bcos2α), then Z α

0

dθ

q

{1−(a1bb)sin2θ}

=p(1−b)

Z β

0

dθ

q

(1−asin2θ) (1−bsin2θ)

(2.3)

Entry 7(iv): If tanα=p(1+x)tanβ, then

Z α

0

dθ

p

(1+xcos 2θ)

=

Z β

0

dθ

q

(1−x2sin4 θ)

(2.4)

which is the correct form of a misprint result of Deniset al.[15, p.115(4)].

Entry 7(v): Degenerate form of addition theorem

If cotαcotβ=p(1−x), then

Z α

0

dθ

q

(1−xsin2θ)

+

Z β

0

dθ

q

(1−xsin2θ)

=π

2 2F1 

   

1 2, 12 ;

x

1 ;

   

(2.5)

Entry 7(vi): Classical duplication formula (Special Case of the converse of Entry 7(viii)a)

If cotαtan(β2) =

q

(1−xsin2α), then

2 Z α

0

dθ

q

(1−xsin2θ)

=

Z β

0

dθ

q

(1−xsin2θ)

(4)

Entry 7(vii): Jacobi’s imaginary transformation (For incomplete elliptic integral of first kind having imag-inary amplitude)

Ifα=ln{tan(π4 +β2)}oreα = 1cossinββ = 1+cossinββ or sinh(α) =tanβ, then

Z iα

0

dθ

q

(1−xsin2θ)

=i

Z β

0

dθ

q

(1−(1−x)sin2θ)

(2.7)

which is the correct form of a misprint result of Deniset al.[15, p.116(7)].

Entry 7(viii): Addition theorem

If

Z α

0

dθ

q

(1−xsin2θ)

+

Z β

0

dθ

q

(1−xsin2θ)

=

Z γ

0

dθ

q

(1−xsin2θ)

(2.8)

then four different sets of hypothesis (implications) are given by

(a) tanγ 2

= sinα

q

(1−xsin2β) +sinβ

q

(1−xsin2α)

cosα+cosβ

which is the correct form of a misprint condition of Deniset al.[15, p.117(i)].

(b) γ=tan−1{tanα

q

(1−xsin2β)}+tan−1{tanβ

q

(1−xsin2α)}

(c) Legendre’s canonical form of the addition theorem

cotαcotβ= cosγ

sinαsinβ

+

q

(1−xsin2γ)

(d)

√ x

2 =

p

{sin(s)sin(s−α)sin(s−β)sin(s−γ)}

sinα sinβsinγ ;where s

= α+β+γ

2

The four different sets of hypothesis (implications)(a)−(d)in Entry 7(viii) are both necessary and sufficient.

Entry 7(xii): Gauss’ transformation

If(1+xsin2α)sinβ= (1+x)sinα, then

(1+x)

Z α

0

dθ

q

(1−x2sin2 θ)

=

Z β

0

dθ

q

{1− 4x

(1+x)2sin

2θ} (2.9)

which is the correct form of misprint result of Deniset al.[15, p.118(9)].

Entry 7(xiii): Landen’s transformation (i.e. The first geometric representation)

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(1+x)

Z α

0

dθ

q

(1−x2sin2 θ)

=2

Z β

0

dθ

q

{1− 4x

(1+x)2sin

2θ} (2.10)

Entries 7(xii) and 7(xiii) are very similar in appearance.

3

A General Family of Multiple-Series Identities

Theorem 3.1. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

sin2m(cθ)dθ

ym

m!

=−ysin(cγ)cos(cγ)

2c

m=0

r=0

Ωm+r+1

(32)m+r(1)rym(ysin2(cγ))r

(2)m+r(2)m+r(32)r

+γ

m=0

Ωm

(12)mym

(m!)2 (3.1) provided that each of the series involved is absolutely convergent.

Theorem 3.2. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

cos2m(cθ)dθ

ym

m!

= ysin(cγ)cos(cγ)

2c

m=0

r=0

Ωm+r+1

(32)m+r(1)rym(ycos2(cγ))r

(2)m+r(2)m+r(32)r

+γ

m=0

Ωm

(12)mym

(m!)2 (3.2) provided that each of the series involved is absolutely convergent.

Theorem 3.3. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

sin4m(cθ)dθ

ym

m! =γ

m=0

Ωm

(14)m(34)mym

(12)m(m!)2 −

−3ysin(cγ)cos(cγ)

8c

m=0

r=0

Ωm+r+1

(54)m+r(74)m+r(1)rym(ysin2(cγ))r

(2)m+r(2)m+r(32)m+r(32)r −

− ysin

3()cos()

4c

m=0

r=0

Ωm+r+1

(54)m+r(47)m+r(2)m+2r(ysin2(cγ))m(ysin4(cγ))r

(2)m+r(2)m+r(32)m+r(52)m+2r

(3.3)

provided that each of the series involved is absolutely convergent.

Theorem 3.4. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

cos4m(cθ)dθ

ym

m! =γ

m=0

Ωm

(14)m(34)mym

(12)m(m!)2 +

+3ysin(cγ)cos(cγ)

8c

m=0

r=0

Ωm+r+1

(54)m+r(74)m+r(1)rym(ycos2(cγ))r

(2)m+r(2)m+r(32)m+r(32)r

+

+ ysin(cγ)cos

3()

4c

m=0

r=0

Ωm+r+1

(54)m+r(47)m+r(2)m+2r(ycos2(cγ))m(ycos4(cγ))r

(2)m+r(2)m+r(32)m+r(52)m+2r

(3.4)

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Theorem 3.5. Let{Λm,n}∞m,n=0be a suitably bounded double sequence of arbitrary complex numbers. Then

m=0

n=0

Λm,n

Z γ

0

sin2m+2n(cθ)dθ

ymzn

m!n!

=γ

m=0

n=0

Λm,n

(12)m+nymzn

(m+n)!m!n! −

zsin(cγ)cos(cγ)

2c

n=0

r=0

Λ0,n+r+1

(32)n+r(1)r zn(zsin2(cγ))r

(2)n+r(2)n+r(32)r −

− ysin(cγ)cos(cγ)

2c

m=0

n=0

r=0

Λm+r+1,n

(32)m+n+r(1)rymzn(ysin2(cγ))r

(2)m+n+r(2)m+r(32)r(1)n −

− yzsin

3()cos()

4c

m=0

n=0

r=0

Λm+1,n+r+1

(52)m+n+r(2)m+r(ysin2(cγ))mzn(zsin2(cγ))r

(3)m+n+r(52)m+r(2)n+r(2)m

(3.5)

provided that each of the series involved is absolutely convergent.

Theorem 3.6. Let{Λm,n}∞m,n=0be a suitably bounded double sequence of arbitrary complex numbers. Then

m=0

n=0

Λm,n

Z γ

0

cos2m+2n(cθ)dθ

ymzn

m!n!

=γ

m=0

n=0

Λm,n

(12)m+nymzn

(m+n)!m!n!+

zsin(cγ)cos(cγ)

2c

n=0

r=0

Λ0,n+r+1

(32)n+r(1)r zn(zcos2(cγ))r

(2)n+r(2)n+r(32)r

+

+ ysin(cγ)cos(cγ)

2c

m=0

n=0

r=0

Λm+r+1,n

(32)m+n+r(1)rymzn(ycos2(cγ))r

(2)m+n+r(2)m+r(32)r(1)n

+

+ yzsin(cγ)cos

3()

4c

m=0

n=0

r=0

Λm+1,n+r+1

(52)m+n+r(2)m+r(ycos2(cγ))mzn(zcos2(cγ))r

(3)m+n+r(52)m+r(2)n+r(2)m

(3.6)

provided that each of the series involved is absolutely convergent.

Theorem 3.7. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

sinm(cθ)dθ

ym m! =γ

m=0

Ω2m

y2m

4m(m!)2 −

y2sin()cos()

4c

m=0

r=0

Ω2m+2r+2

(1)ry2m(ysin(cγ))2r

4m+r(2)m

+r(2)m+r(32)r

+

+y

c

m=0

Ω2m+1

y2m

4m(3 2)m(32)m

−ycos(cγ) c

m=0

r=0

Ω2m+2r+1

(12)ry2m(ysin(cγ))2r

4m+r(3

2)m+r(32)m+r(1)r

(3.7)

provided that each of the series involved is absolutely convergent.

Theorem 3.8. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

cosm(cθ)dθ

ym m! =γ

m=0

Ω2m y 2m

4m(m!)2 +

y2sin(cγ)cos(cγ)

4c

m=0

r=0

Ω2m+2r+2

(1)ry2m(ycos(cγ))2r

4m+r(2)

m+r(2)m+r(32)r

+

+ysin(cγ)

c

m=0

r=0

Ω2m+2r+1

(12)ry2m(ycos(cγ))2r

4m+r(3

2)m+r(32)m+r(1)r

(3.8)

(7)

Theorem 3.9. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

sin2m+1(cθ)dθ

ym

m! =

1

c

m=0

Ωm y m

(32)m

cos(cγ)

c

m=0

r=0

Ωm+r

(12)r ym(ysin2(cγ))r

(32)m+r(1)r

(3.9)

provided that each of the series involved is absolutely convergent.

Theorem 3.10. Let{Ωm}∞m=0be a suitably bounded sequence of arbitrary complex numbers. Then

m=0

Ωm

Z γ

0

cos2m+1(cθ)dθ

ym

m! =

sin(cγ)

c

m=0

r=0

Ωm+r

(12)r ym(ycos2(cγ))r

(32)m+r(1)r

(3.10)

provided that each of the series involved is absolutely convergent.

Theorem 3.11. Let{Λm,n}∞m,n=0be a suitably bounded double sequence of arbitrary complex numbers. Then

m=0

n=0

Λm,n

Z γ

0

sin2m+2n+1(cθ)dθ

ymzn

m!n!

=−cos(cγ) c

m=0

n=0

r=0

Λm+r,n

(1)m+n+r(12)rymzn(ysin2(cγ)) r

(32)m+n+r(1)m+r(1)n (1)r

− zcos(cγ)sin 2()

3c

m=0

n=0

r=0

Λm,n+r+1

(2)m+n+r(32)m+r(ysin2(cγ))mzn(zsin2(cγ))r (52)m+n+r(2)n+r(2)m+rm! +

+ 1

c

m=0

n=0

Λm,n

(1)m+nymzn

(32)m

+nm!n!

(3.11)

provided that each of the series involved is absolutely convergent.

Theorem 3.12. Let{Λm,n}∞m,n=0be a suitably bounded double sequence of arbitrary complex numbers. Then

m=0

n=0

Λm,n

Z γ

0

cos2m+2n+1(cθ)dθ

ymzn

m!n!

= sin(cγ)

c

m=0

n=0

r=0

Λm+r,n

(1)m+n+r(12)rymzn(ycos2(cγ))r

(32)m

+n+r(1)m+r(1)n(1)r

+

+ zsin(cγ)cos

2()

3c

m=0

n=0

r=0

Λm,n+r+1

(2)m+n+r(32)m+r(ycos2(cγ))mzn(zcos2(cγ))r

(52)m+n+r(2)m+r(2)n+r m! (3.12)

provided that each of the series involved is absolutely convergent.

Proof of (3.1): ∞

m=0

Ωm

Z γ

0

sin2m(cθ)dθ

ym

m!

=−

m=0 m−1

r=0

Ωmsin

(cγ)cos(cγ)(12)m(1)rym(sin2(cγ))r c(1)m(1)m(32)r

+γ

m=0

Ωm

(12)mym

(m!)2

=−

∞ m=0

m

r=0

Ωm+1

sin(cγ)cos(cγ)(12)m+1(1)r ym+1(sin2(cγ))r

c(1)m+1(1)m+1(32)r +γ

m=0

Ωm

(12)mym

(m!)2

=−ysin(cγ)cos(cγ)

2c

m=0

r=0

Ωm+r+1

(32)m+r(1)rym(ysin2(cγ))r

(2)m+r(2)m+r(32)r

+γ

m=0

Ωm

(12)mym

(m!)2

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4

Hypergeometric Generalizations of Incomplete Elliptic Integrals of Ramanujan and

their solutions

Puttingc=1 in theorems (3.1) to (3.6), (3.9) to (3.12) and setting

Ωm=

(a1)m(a2)m(a3)m· · ·(aA)m

(b1)m(b2)m(b3)m· · ·(bB)m

= ((aA))m ((bB))m, Λm,n

= ((aA))m+n((dD))m((gG))n ((bB))m+n((eE))m((hH))n ,

in theorems (3.1) to (3.12), using some algebraic properties of Pochhammer symbol and interpreting the

mul-tiple power series in hypergeometric forms of Gauss [34, p. 42(1)], Kamp´e de F´eriet [34, p.63(16); see also 33],

Srivastava [34, p.69(39,40)] and Srivastava-Daoust [33, p.37(21, 22, 23); 34, pp.64-65(18, 19, 20)], we get the

analytical solutions of generalized incomplete elliptic integrals.

Z γ

0 A FB

   

(aj)Aj=1 ;

ysin2θ

(bj)Bj=1 ;

   

dθ=γA+1FB+1

   

1

2,(aj)Aj=1 ; y

1,(bj)Bj=1 ;

   

ysinγcosγ

A

i=1

(ai)

2∏B

i=1

(bi)

FBA++21::01;;12

   

3

2,(1+aj)Aj=1 :1 ;1, 1 ;

y,ysin2γ

2, 2,(1+bj)Bj=1: ;32 ;

   

(4.1)

Z γ

0 A FB

   

(aj)jA=1 ;

ycos2θ

(bj)Bj=1 ;

   

dθ=γA+1FB+1

   

1

2,(aj)Aj=1 ; y

1,(bj)Bj=1 ;

   

+

+

ysinγ cosγ

A

i=1

(ai)

2 ∏B

i=1

(bi)

FBA++21::01;1;2

   

3

2,(1+aj)Aj=1 :1 ;1 , 1 ;

y,ycos2γ

2, 2,(1+bj)Bj=1: ; 32 ;

   

(4.2)

Z γ

0 A

FB

   

(aj)Aj=1 ;

ysin4θ

(bj)Bj=1 ;

   

dθ=γA+2FB+2

   

1

4,34,(aj)jA=1 ; y

1,12,(bj)Bj=1 ;

   

3y sinγcosγ A

i=1

(ai)

8∏B

i=1

(bi)

FBA++32::01;1;2

   

5

4,74,(1+aj)Aj=1 : 1; 1, 1 ;

y,ysin2γ

2, 2,32,(1+bj)Bj=1: ; 32 ;

   

ysin3γ cosγ

A

i=1

(ai)

4∏B

i=1

(bi)

FBA++43:0:1;;01

   

[(1+aj):1, 1]jA=1, [54:1, 1], [74:1, 1], [2:1, 2] :

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[1:1];[1:1] ;

ysin2γ,ysin4γ

; ;

   

(4.3)

Z γ

0 A

FB

   

(aj)Aj=1 ;

ycos4θ

(bj)Bj=1 ;

   

dθ=γA+2FB+2

   

1

4,34,(aj)Aj=1 ; y

1,12,(bj)Bj=1 ;

   

+

+

3y sinγcosγ A

i=1

(ai)

8 ∏B

i=1

(bi)

FBA++32:0:1;;12

   

5

4,74,(1+aj)Aj=1 : 1;1, 1 ;

y,ycos2γ

2, 2,32,(1+bj)Bj=1: ;32 ;

   

+

+

ysinγcos3γ

A

i=1

(ai)

4∏B

i=1

(bi)

FBA++43:0:1;;01

   

[(1+aj):1, 1]Aj=1, [54:1, 1], [74:1, 1], [2:1, 2] :

[(1+bj):1, 1]jB=1,[2:1, 1],[2:1, 1],[32:1, 1],[52:1, 2] :

[1:1];[1:1] ;

ycos2γ,ycos4γ

; ;

   

(4.4)

Z γ

0

FBA::ED;H;G

   

(aj)Aj=1:(dj)Dj=1;(gj)Gj=1 ;

ysin2θ,zsin2θ

(bj)Bj=1:(ej)jE=1;(hj)Hj=1 ;

   

dθ

=γ FBA++11:E:D;H;G

   

(aj)Aj=1, 12:(dj)Dj=1;(gj)Gj=1 ;

y,z

(bj)Bj=1, 1:(ej)Ej=1;(hj)Hj=1 ;

   

zsinγcosγ

A

i=1

(ai) G

i=1

(gi)

2∏B

i=1

(bi) H

i=1

(hi)

×

× FBA++HG++21::01;;12

   

3

2,(1+aj)Aj=1,(1+gj)Gj=1 : 1;1, 1 ;

z,zsin2γ

2, 2, (1+bj)Bj=1,(1+hj)Hj=1: ; 32 ;

   

y sinγcosγ

A

i=1

(ai) D

i=1

(di)

2∏B

i=1

(bi) E

i=1

(ei)

×

×F(3)

   

3

2,(1+aj)jA=1:: ; ;(1+dj)Dj=1 :1;(gj)Gj=1;1, 1 ;

y,z,ysin2γ

2,(1+bj)Bj=1:: ; ;(1+ej)Ej=1, 2: ;(hj)Hj=1;32 ;

   

(10)

y zsin3γ cosγ

A

i=1

(ai) A

i=1

(1+ai) D

i=1

(di) G

i=1

(gi)

4 ∏B

i=1

(bi) ∏B

i=1

(1+bi) ∏E

i=1

(ei) ∏H

i=1

(hi)

×

×F(3)

   

5

2,(2+aj)Aj=1:: ;(1+gj)Gj=1 ;2:1,(1+dj)Dj=1;1;1 ;

ysin2γ,z,zsin2γ

3,(2+bj)Bj=1:: ;(1+hj)Hj=1, 2;52:2,(1+ej)Ej=1; ; ;

   

(4.5)

Z γ

0

FBA::ED;H;G

   

(aj)Aj=1:(dj)Dj=1;(gj)Gj=1 ;

ycos2θ,zcos2θ

(bj)Bj=1:(ej)Ej=1;(hj)Hj=1 ;

   

dθ

=γFBA++11:E:D;H;G

   

(aj)jA=1, 12:(dj)Dj=1;(gj)Gj=1 ;

y,z

(bj)Bj=1, 1:(ej)Ej=1;(hj)jH=1 ;

   

+

zsinγcosγ

A

i=1

(ai) G

i=1

(gi)

2 ∏B

i=1

(bi) ∏H

i=1

(hi)

×

×FBA++HG++21::01;;12

   

3

2,(1+aj)Aj=1,(1+gj)Gj=1 : 1;1, 1 ;

z,zcos2γ

2, 2, (1+bj)Bj=1,(1+hj)Hj=1: ; 32 ;

   

+

+

ysinγ cosγ

A

i=1

(ai) D

i=1

(di)

2 ∏B

i=1

(bi) E

i=1

(ei)

×

×F(3)

   

3

2,(1+aj)jA=1:: ; ;(1+dj)Dj=1 :1;(gj)Gj=1; 1, 1 ;

y,z,ycos2γ

2, (1+bj)jB=1:: ; ;(1+ej)Ej=1, 2: ;(hj)Hj=1; 32 ;

   

+

+

y zsinγcos3γ

A

i=1

(ai) A

i=1

(1+ai) D

i=1

(di) G

i=1

(gi)

4 ∏B

i=1

(bi) B

i=1

(1+bi) E

i=1

(ei) H

i=1

(hi)

F(3)

   

5

2,(2+aj)Aj=1:: ;(1+gj)Gj=1 ;2:

3,(2+bj)Bj=1:: ;(1+hj)Hj=1, 2 ;52:

1,(1+dj)Dj=1; 1 ; 1 ;

ycos2γ,z,zcos2γ

2,(1+ej)Ej=1; ; ;

   

(4.6)

Z γ

0 A FB

   

(aj)jA=1 ;

ysin(cθ)

(bj)Bj=1 ;

   

(11)

=γ2AF2B+1

   

(a2j)jA=1,(1+2aj)Aj=1 ;

y2 4(1+B−A)

1,(b2j)Bj=1,(1+2bj)Bj=1 ;

   

ycos(cγ)

A

i=1

(ai)

c ∏B

i=1

(bi) ×

×F2B2A+2::10;;10

   

(1+2aj)jA=1,(2+2aj)Aj=1 :1;12 ;

y2

4(1+B−A),

y2sin2(c

γ)

4(1+B−A)

3 2, 32,(

1+bj 2 )Bj=1,(

2+bj

2 )Bj=1: ; ;

   

y2sin(cγ)cos(cγ)A

i=1

(ai)A

i=1

(1+ai)

4c ∏B

i=1

(bi) B

i=1

(1+bi)

×

×F2B2A+2::10;;21

   

(2+2aj)jA=1,(3+2aj)jA=1 :1;1, 1 ;

y2

4(1+B−A),

y2sin2(c

γ)

4(1+B−A)

2, 2,(2+2bj)Bj=1,(3+2bj)Bj=1: ; 32 ;

   

+

+

y ∏A

i=1

(ai)

c∏B

i=1

(bi)

2A+1F2B+2

   

1,(1+2aj)Aj=1,(2+2aj)Aj=1 ;

y2

4(1+B−A)

3 2, 32,(

1+bj 2 )Bj=1,(

2+bj 2 )Bj=1 ;

   

(4.7)

Z γ

0 A FB

   

(aj)Aj=1 ;

ycos(cθ)

(bj)Bj=1 ;

   

dθ

=γ2AF2B+1

   

(a2j)jA=1,(1+2aj)jA=1 ;

y2

4(1+B−A)

1,(b2j)Bj=1,(1+2bj)Bj=1 ;

   

+

ysin(cγ)

A

i=1

(ai)

c ∏B

i=1

(bi) ×

×F2B2A+2::10;;10

   

(1+2aj)Aj=1,(2+2aj)Aj=1 :1; 12 ;

y2

4(1+B−A),

y2cos2(cγ)

4(1+B−A)

3 2, 32,(

1+bj 2 )Bj=1,(

2+bj

2 )Bj=1: ; ;

   

+

+

y2sin(cγ)cos(cγ)A

i=1

(ai) A

i=1

(1+ai)

4c ∏B

i=1

(bi) B

i=1

(1+bi)

×

×F2B2A+2::10;;21

   

(2+2aj)Aj=1,(3+2aj)Aj=1 :1;1, 1 ;

y2

4(1+B−A),

y2cos2(cγ)

4(1+B−A)

2, 2, (2+2bj)Bj=1,(3+2bj)Bj=1: ;32 ;

   

(12)

Z γ

0

sinθAFB

   

(aj)jA=1 ;

ysin2θ

(bj)Bj=1 ;

   

dθ=A+1FB+1

   

1,(aj)Aj=1 ; y

3

2,(bj)Bj=1 ;

   

− cosγFBA+1::10;;10

   

(aj)Aj=1 :1 ; 12 ;

y, ysin2γ

3

2,(bj)Bj=1: ; ;

   

(4.9)

Z γ

0

cosθAFB

   

(aj)Aj=1 ;

ycos2θ

(bj)Bj=1 ;

   

dθ=sinγFBA+1::10;;10

   

(aj)Aj=1 :1 ; 12 ;

y,ycos2γ

3

2,(bj)Bj=1: ; ;

   

(4.10)

Z γ

0

sinθFBA::ED;H;G

   

(aj)jA=1:(dj)Dj=1;(gj)Gj=1 ;

ysin2θ,zsin2θ

(bj)Bj=1:(ej)jE=1;(hj)Hj=1 ;

   

dθ

=FBA++11::ED;H;G

   

1, (aj)Aj=1:(dj)Dj=1;(gj)Gj=1 ;

y,z

3

2,(bj)Bj=1:(ej)Ej=1;(hj)Hj=1 ;

   

− cosγF(3)

   

1, (aj)Aj=1:: ; ;(dj)Dj=1 :1;(gj)Gj=1; 12 ;

y,z,ysin2γ 3

2,(bj)Bj=1:: ; ;1,(ej)Ej=1: ;(hj)jH=1; ;

   

zsin2γcosγ

A

i=1

(ai) G

i=1

(gi)

3 ∏B

i=1

(bi) H

i=1

(hi)

×

×F(3)

   

2,(1+aj)Aj=1:: ;(1+gj)Gj=1 ; 32:(dj)Dj=1; 1 ; 1 ;

ysin2γ,z,zsin2γ

5

2,(1+bj)jB=1:: ;2,(1+hj)Hj=1;2:(ej)Ej=1; ; ;

   

(4.11)

Z γ

0

cosθFBA::ED;H;G

   

(aj)jA=1:(dj)Dj=1;(gj)Gj=1 ;

ycos2θ,zcos2θ

(bj)Bj=1:(ej)jE=1;(hj)Hj=1 ;

   

dθ

=sinγF(3)

   

1,(aj)jA=1:: ; ;(dj)Dj=1 :1;(gj)Gj=1; 12 ;

y,z,ycos2γ

3

2,(bj)Bj=1:: ; ;1,(ej)Ej=1: ;(hj)Hj=1; ;

   

+

+

zsinγcos2γ

A

i=1

(ai) ∏G

i=1

(gi)

3 ∏B

i=1

(bi) H

i=1

(hi)

(13)

×F(3)

   

2, (1+aj)jA=1:: ; (1+gj)jG=1 ;32:(dj)Dj=1; 1; 1 ;

ycos2γ,z,zcos2γ

5

2,(1+bj)Bj=1:: ;2, (1+hj)Hj=1;2:(ej)Ej=1 ; ; ;

   

(4.12)

provided that each of the series as well as associated integrals involved are convergent.

5

Solutions of Ramanujan’s incomplete elliptic integrals

SettingA=1,B=0 anda1= 12in (4.1) and (4.2) respectively, we get

F(√y,γ) =

Z γ

0

dθ

q

(1−ysin2θ)

=γ2F1

   

1 2,12 ;

y

1 ;

   

−ysinγ cosγ

4 ×

×F22::01;;12

   

3

2,32:1;1, 1 ;

y,ysin2γ

2, 2: ; 32 ;

   

;|y|<1 (5.1)

which is the exact solution of incomplete elliptic integral of first kind.

Z γ

0

dθ

p

(1−ycos2θ) =γ2F1

   

1 2,12 ;

y

1 ;

   

+ysinγcosγ

4 ×

×F22::01;;12

   

3

2,32:1;1, 1 ;

y,ycos2γ

2, 2: ; 32 ;

   

;|y|<1 (5.2)

Puttingγ= π2 in (5.1) and (5.2), we get

K(√y) =

Z π2

0

dθ

q

(1−ysin2θ)

=

Z π2

0

dθ

p

(1−ycos2θ) = π

2 2F1 

   

1 2,12 ;

y

1 ;

   

;|y|<1 (5.3)

which is well-known complete elliptic integral of first kind.

PuttingA=1,B=0 anda1=−12in (4.1)and (4.2)respectively, we get

E(√y,γ) =

Z γ

0

q

(1−ysin2θ)dθ=γ2F1

   

1 2,−12 ;

y

1 ;

   

+ysinγcosγ

(14)

×F22::01;;12

   

1

2,32:1;1, 1 ;

y,ysin2γ

2, 2: ; 32 ;

   

;|y|<1 (5.4)

which is the exact solution of incomplete elliptic integral of second kind.

Z γ

0

q

(1−ycos2θ)dθ=γ2F1

   

1 2,−12 ;

y

1 ;

   

−ysinγcosγ

4 ×

×F22::01;;12

   

1

2,32:1;1, 1 ;

y,ycos2γ

2, 2: ; 32 ;

   

;|y|<1 (5.5)

Settingγ= π2 in (5.4) and (5.5), we get

E(√y) =

Z π2

0

q

(1−ysin2θ)dθ=

Z π2

0

q

(1−ycos2θ)dθ= π

2 2F1 

   

−12,12 ;

y

1 ;

   

;|y|<1 (5.6)

which is well-known complete elliptic integral of second kind.

PuttingA=1,B=0, a1= 21, γ=βandy=x2in (4.3), we get

Z β

0

dθ

q

(1−x2sin4 θ)

=β2F1

   

1 4,34 ;

x2

1 ;

   

− 3x

2 sinβcosβ

16 ×

×F22::01;;12

   

5

4,74:1;1, 1 ;

x2,x2 sin2 β

2, 2: ; 32 ;

   

− x 2 sin3

βcosβ

8 ×

×F33::01;;01

   

[54:1, 1],[74:1, 1],[2:1, 2]: [1:1]; [1:1] ;

x2sin2β,x2sin4β

[2:1, 1],[2:1, 1],[52:1, 2] : ; ;

   

;|x|<1 (5.7)

which is the exact solution of unsolved-incomplete elliptic integral given in Ramanujan’s Entry 7(iv).

SettingA=B=E=H=0, D=G=1, d1=g1= 12, γ=β, y=a, z=bin (4.5), we get

Z β

0

dθ

q

(1−asin2θ) (1−bsin2θ)

=βF11::10;;10

   

1

2: 12; 12 ; a,b

1: ; ;

   

−b sinβcosβ

4 F

2:1;2 2:0;1

   

3

2, 32: 1;1, 1 ;

b,bsin2β

2, 2: ; 32 ;

   

(15)

−asinβcosβ

4 F

(3)

   

3

2:: ; ;32 :1;12;1, 1 ;

a,b,asin2β

2:: ; ;2: ; ; 32 ;

   

− a bsin

3βcosβ

16 F

(3)

   

5

2:: ;32;2:1,32;1;1 ;

asin2β,b,bsin2β

3:: ;2 ;52:2; ; ;

   

;max{|a|,|b|}<1 (5.8)

which is the exact solution of unsolved-incomplete elliptic integral given in Ramanujan’s Entry 7(iii). Here

F1:0;01:1;1[·]is Appell’s function of first kind, in the notation of Srivastava and Panda.

SettingA=B=E=H=0, D=G=1, d1=1, g1= 12, γ=φ, y=a, z=b2in (4.5), we get

(a, b, φ) =

Z φ

0

dθ

(1−asin2θ)

q

(1−b2sin2 θ)

=φF11::01;;01

   

1

2:1; 12 ; a,b2

1: ; ;

   

−b 2 sin

φcosφ

4 F

2:1;2 2:0;1

   

3

2, 32 :1 ; 1, 1 ;

b2,b2sin2φ

2, 2 : ;32 ;

   

− asinφcosφ

2 F

(3)

   

3

2:: ; ; :1 ; 12 ;1, 1 ;

a,b2,asin2 φ

2:: ; ; : ; ;32 ;

   

− a b

2 sin3φcosφ

8 F

(3)

   

5

2 :: ;32;2:1 ;1 ;1 ;

asin2φ,b2,b2sin2φ

3:: ;2;52 : ; ; ;

   

(5.9)

where max{|a|,|b|}<1

which is the exact solution of incomplete elliptic integral of third kind.

In (5.9), puttingφ= π2 we get the exact solution of complete elliptic integral of third kind.

a, b, π 2

=

Z π2

0

dθ

(1−asin2θ)

q

(1−b2sin2θ)

= π

2 F1 1

2;1, 1 2;1;a,b

2

;max{|a|,|b|}<1 (5.10)

whereF1

1

2;1,12;1;a,b2

is Appell’s function of first kind[34,p.53(1.6.4)].

These solutions are not found in Ramanujan’s notebooks[29-31], Five notebooks of B. C. Berndt [6-10],

Three volumes of R. P. Agarwal [2-4] and other literature [5; 17; 18; 20; 22(pp.100-106); 24; 25; 26; 28; 32; 35] on

(16)

SettingA=1, B=0, a1= 12, γ=α, y=−x, c=2 in (4.8), we get

Z α

0

dθ

p

(1+xcos 2θ)

=α2F1

   

1 4, 34 ;

x2

1, ;

   

− xsin(2α)

4 ×

×F22::01;;01

   

3

4, 54:1;12 ;

x2,x2cos2(2α) 3

2, 32: ; ;

   

+

+3x

2sin(4α)

64 F

2:1;2 2:0;1

   

5

4, 74:1;1, 1 ;

x2,x2cos2(2α)

2, 2: ; 32 ;

   

;|x|<1 (5.11)

Further on using (5.2) in above integral, we get an elegant formula in the following form:

p

(1−x)

Z α

0

dθ

p

(1+xcos 2θ)

=

Z α

0

dθ

q

{1−(x2x1)cos2θ)}

=α2F1

   

1 2,12 ;

2x x−1

1 ;

   

+ xsin 2α

4(x−1) F

2:1;2 2:0;1

   

3

2,32:1;1, 1 ; 2x x−1, 2xcos

2α

x−1

2, 2: ;32 ;

   

;

2x

x−1

<1 (5.12)

which is the exact solution of Ramanujan’s unsolved-incomplete elliptic integral given in Entry 7(iv).

6

Special cases

In (4.1), setA=2,B=1,a1=b,a2=1−b,b1=12 andγ= π2, we obtain

Z π2

0

cos{(2b−1)sin−1(√ysinθ)}

q

(1−ysin2θ)

dθ= π

2 2F1 

   

b, 1−b ;

y

1 ;

   

(6.1)

which is the known result of Ramanujan [8, p.88(Entry 1)].

In (4.1), putA=2,B=1,a1=13,a2= 23,b1= 12andγ= π2, we obtain

Z π2

0 2 F1

   

1 3, 23 ;

ysin2θ

1

2 ;

   

dθ= π

2 2F1 

   

1 3, 23 ;

y

1 ;

   

(6.2)

(17)

In (5.7), setβ= π2 andx2=y, we have

Z π2

0

dθ

q

(1−y sin4θ)

= π

2 2F1 

   

1 4,34 ;

y

1 ;

   

(6.3)

which is another known result of B.C.Berndt[8, p.110].

References

[1] Abramowitz, M. and Stegun, I. A.;Handbook of Mathematical Functions with Formulas Graphs and

Mathe-matical Tables,Appl. Math. Ser. 55. U. S. Govt. Printing Office, National Bureau of Standards, Washington

D. C., 1964.; Reprinted by Dover Publications, Inc., New York, 1965.

[2] Agarwal, R. P.;Resonance of Ramanujan’s Mathematics,Vol. I, New Age International(P) Ltd., New Delhi,

1996.

[3] Agarwal, R. P.;Resonance of Ramanujan’s Mathematics,Vol. II, New Age International(P) Ltd., New Delhi,

1996.

[4] Agarwal, R. P.;Resonance of Ramanujan’s Mathematics,Vol. III, New Age International(P) Ltd., New Delhi,

1999.

[5] Andrews, G. E. and Berndt, B. C.;Ramanujan’s Lost Notebook, Part I, Springer-Verlag, New York, 2005.

[6] Berndt, B. C.;Ramanujan’s Notebooks,Part I, Springer-Verlag, New York, 1985.

[7] Berndt, B. C.;Ramanujan’s Notebooks,Part II, Springer-Verlag, New York 1989.

[8] Berndt, B. C.;Ramanujan’s Notebooks,Part III, Springer-Verlag, New York, 1991.

[9] Berndt, B. C.;Ramanujan’s Notebooks,Part IV, Springer-Verlag, New York 1994.

[10] Berndt, B. C.;Ramanujan’s Notebooks,Part V, Springer-Verlag, New York 1998.

[11] Byrd, P. F. and Friedman, M. D.;Handbook of Elliptic Integrals for Engineers and Scientists, Springer -Verlag,

Heidelberg, 1971.

[12] Carlson, B. C.; Some Series and Bounds for Incomplete Elliptic Integral,J. Math. Phys.,40(1961), 125-134.

[13] Carlson, B. C.; Normal Elliptic Integrals of the First and Second Kinds,Duke Math. J.,31(1964), 405-419.

[14] Chaudhary, M. P.;On Certain Aspects of Generalized Special Functions and Integral Operators,Doctoral thesis

approved for Ph.D. degree, J.M.I.(A Central University), New Delhi, India, 2011.

[15] Denis, R. Y., Singh, S. N. and Singh, S. P.; On Certain Elliptic Integrals of Ramanujan,J. Indian Math. Soc.,

(18)

[16] Dutka, J.; Two Results of Ramanujan,Siam J. Math. Anal.,12(1981), 471-476.

[17] Erd´elyi, A., Magnus, W., Oberhettinger, F. and Tricomi, F. G.; Higher Transcendental Functions, Vol.

II(Bateman Manuscript Project), McGraw-Hill, Book Co. Inc., New York, Toronto and London, 1953.

[18] Gradshteyn, I. S. and Ryzhik, I. M.;Table of Integrals, Series and Products,Fourth Edition, 1965, Corrected

and Enlarged Edition by A. Jeffrey 1980, 5thEd. by A. Jeffrey, Academic Press, New York, 1994.

[19] Hansen, E.R.;A Table of Series and Product, Prentice Hall, Engle-Wood Cliffs, New Jersey, 1975.

[20] Hardy, G. H., Aiyer, P. V. Seshu and Wilson, B. M.;Collected Papers of Srinivasa Ramanujan,First Published

by Cambridge University Press, Cambridge, 1927; Reprinted by Chelsea, New York, 1962; Reprinted by

the American Mathematical Society, Providence, Rhode Island, 2000.

[21] Jahnke, E. and Emde, F.;Tables of Functions with Formulas and Curves, Fourth Edition, Dover Publications,

Inc., New York, 1945.

[22] Jahnke, E., Emde, F. and L ¨osch, F.;Tables of Higher Functions, Sixth Edition, McGraw-Hill, New York, 1960.

[23] Jeffrey, A.;Handbook of Mathematical Formulas and Integrals, Second Edition, Academic Press, San Diego,

San Francisco, New York, Boston, London, Sydney and Tokyo, 2000.

[24] Magnus, W., Oberhettinger, F. and Soni, R. P.;Formulas and Theorems for the Special Function of Mathematical

Physics, Springer-Verlag, New York, 1966.

[25] Montaldi, E. and Zucchelli, G.; Some Formulas of Ramanujan Revisited,SIAM J. Math. Anal.,23(1992), 562-569.

[26] Pathan, M. A.; Some Formulas of Ramanujan on Hypergeometric Series, The Math. Student, 72(2003),

31-44.

[27] Prudnikov, A. P., Brychkov, Yu. A. and Marichev, O. I.;Integrals and Series, Vol 3., More Special

Func-tions, Nauka, Moscow, 1986; Translated from the Russian by G. G. Gould; Gordon and Breach Science

Publishers, New York, Philadelphia, London, Paris, Montreux, Tokyo, Melbourne, 1990.

[28] Raghavan, S. and Rangachari, S. S.; On Ramanujan’s Elliptic Integrals and Modular Identities inNumber

Theory and Related Topics, Oxford University Press, Bombay, 1989, 119-149.

[29] Ramanujan, S.;Notebooks of Srinivasa Ramanujan,Vol. I, Tata Institute of Fundamental Research, Bombay,

1957; Reprinted by Narosa Publishing House, New Delhi, 1984.

[30] Ramanujan, S.;Notebooks of Srinivasa Ramanujan,Vol. II, Tata Institute of Fundamental Research, Bombay,

1957; Reprinted by Narosa Publishing House, New Delhi, 1984.

[31] Ramanujan, S.;The Lost Notebook and Other Unpublished Papers,Narosa Publishing House, New Delhi,

(19)

[32] Rao, K. Srinivasa;Srinivasa Ramanujan: A Mathematical Genius,East West Books (Madras) Pvt. Ltd.,

Chen-nai, Bangalore, Hyderabad, 1998.

[33] Srivastava, H. M. and Karlsson, Per W.; Multiple Gaussian Hypergeometric Series, Halsted Press (Ellis

Horwood Ltd., Chichester, Brisbane, U. K.) John Wiley and Sons, New York, Chichester, Brisbane and

Toronto, 1985.

[34] Srivastava, H. M. and Manocha, H. L.;A Treatise on Generating Functions, Halsted Press (Ellis Horwood

Ltd., Chichester, Brisbane, U. K.) John Wiley and Sons, New York, Chichester, Brisbane and Toronto, 1984.

[35] Venkatchala, B. J., Vinay, V. and Yogananda, C. S.;Ramanujan’s Papers,Prism Books Pvt. Ltd., Bangalore,

Mumbai, India, 2000.

Received: March 14, 2014;Accepted: August 23, 2014

UNIVERSITY PRESS

References

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