Appendix E
Properties of special functions
E.1 Bessel functions
Notation
z = complex number; ν,x = real numbers; n = integer
J
ν
(z) = ordinary Bessel function of the ?rst kind
N
ν
(z) = ordinary Bessel function of the second kind
I
ν
(z) = modi?ed Bessel function of the ?rst kind
K
ν
(z) = modi?ed Bessel function of the second kind
H
(1)
ν
= Hankel function of the ?rst kind
H
(2)
ν
= Hankel function of the second kind
j
n
(z) = ordinary spherical Bessel function of the ?rst kind
n
n
(z) = ordinary spherical Bessel function of the second kind
h
(1)
n
(z) = spherical Hankel function of the ?rst kind
h
(2)
n
(z) = spherical Hankel function of the second kind
f
prime
(z) = df(z)/dz = derivative with respect to argument
Di?erentialequations
d
2
Z
ν
(z)
dz
2
+
1
z
dZ
ν
(z)
dz
+
parenleftbigg
1 ?
ν
2
z
2
parenrightbigg
Z
ν
(z) = 0 (E.1)
Z
ν
(z) =
?
?
?
?
?
?
?
J
ν
(z)
N
ν
(z)
H
(1)
ν
(z)
H
(2)
ν
(z)
(E.2)
N
ν
(z) =
cos(νπ)J
ν
(z)? J
?ν
(z)
sin(νπ)
,νnegationslash= n, |arg(z)| <π (E.3)
H
(1)
ν
(z) = J
ν
(z)+ jN
ν
(z) (E.4)
H
(2)
ν
(z) = J
ν
(z)? jN
ν
(z) (E.5)
d
2
ˉ
Z
ν
(x)
dz
2
+
1
z
d
ˉ
Z
ν
(z)
dz
?
parenleftbigg
1 +
ν
2
z
2
parenrightbigg
ˉ
Z
ν
= 0 (E.6)
ˉ
Z
ν
(z) =
braceleftbigg
I
ν
(z)
K
ν
(z)
(E.7)
L(z) =
braceleftbigg
I
ν
(z)
e
jνπ
K
ν
(z)
(E.8)
I
ν
(z) = e
?jνπ/2
J
ν
(ze
jπ/2
), ?π<arg(z) ≤
π
2
(E.9)
I
ν
(z) = e
j3νπ/2
J
ν
(ze
?j3π/2
),
π
2
< arg(z) ≤ π (E.10)
K
ν
(z) =
jπ
2
e
jνπ/2
H
(1)
ν
(ze
jπ/2
), ?π<arg(z) ≤
π
2
(E.11)
K
ν
(z) =?
jπ
2
e
?jνπ/2
H
(2)
ν
(ze
?jπ/2
), ?
π
2
< arg(z) ≤ π (E.12)
I
n
(x) = j
?n
J
n
(jx) (E.13)
K
n
(x) =
π
2
j
n+1
H
(1)
n
(jx) (E.14)
d
2
z
n
(z)
dz
2
+
2
z
dz
n
(z)
dz
+
bracketleftbigg
1 ?
n(n + 1)
z
2
bracketrightbigg
z
n
(z) = 0, n = 0,±1,±2,... (E.15)
z
n
(z) =
?
?
?
?
?
?
?
j
n
(z)
n
n
(z)
h
(1)
n
(z)
h
(2)
n
(z)
(E.16)
j
n
(z) =
radicalbigg
π
2z
J
n+
1
2
(z) (E.17)
n
n
(z) =
radicalbigg
π
2z
N
n+
1
2
(z) (E.18)
h
(1)
n
(z) =
radicalbigg
π
2z
H
(1)
n+
1
2
(z) = j
n
(z)+ jn
n
(z) (E.19)
h
(2)
n
(z) =
radicalbigg
π
2z
H
(2)
n+
1
2
(z) = j
n
(z)? jn
n
(z) (E.20)
n
n
(z) = (?1)
n+1
j
?(n+1)
(z) (E.21)
Orthogonalityrelationships
integraldisplay
a
0
J
ν
parenleftBig
p
νm
a
ρ
parenrightBig
J
ν
parenleftBig
p
νn
a
ρ
parenrightBig
ρ dρ = δ
mn
a
2
2
J
2
ν+1
(p
νn
) = δ
mn
a
2
2
bracketleftbig
J
prime
ν
(p
νn
)
bracketrightbig
2
,ν>?1
(E.22)
integraldisplay
a
0
J
ν
parenleftbigg
p
prime
νm
a
ρ
parenrightbigg
J
ν
parenleftbigg
p
prime
νn
a
ρ
parenrightbigg
ρ dρ = δ
mn
a
2
2
parenleftbigg
1 ?
ν
2
p
prime2
νm
parenrightbigg
J
2
ν
(p
prime
νm
), ν > ?1 (E.23)
integraldisplay
∞
0
J
ν
(αx)J
ν
(βx)xdx=
1
α
δ(α?β) (E.24)
integraldisplay
a
0
j
l
parenleftBig
α
lm
a
r
parenrightBig
j
l
parenleftBig
α
ln
a
r
parenrightBig
r
2
dr = δ
mn
a
3
2
j
2
n+1
(α
ln
a) (E.25)
integraldisplay
∞
?∞
j
m
(x)j
n
(x) dx = δ
mn
π
2n + 1
, m, n ≥ 0 (E.26)
J
m
(p
mn
) = 0 (E.27)
J
prime
m
(p
prime
mn
) = 0 (E.28)
j
m
(α
mn
) = 0 (E.29)
j
prime
m
(α
prime
mn
) = 0 (E.30)
Speci?cexamples
j
0
(z) =
sin z
z
(E.31)
n
0
(z) =?
cos z
z
(E.32)
h
(1)
0
(z) =?
j
z
e
jz
(E.33)
h
(2)
0
(z) =
j
z
e
?jz
(E.34)
j
1
(z) =
sin z
z
2
?
cos z
z
(E.35)
n
1
(z) =?
cos z
z
2
?
sin z
z
(E.36)
j
2
(z) =
parenleftbigg
3
z
3
?
1
z
parenrightbigg
sin z ?
3
z
2
cos z (E.37)
n
2
(z) =
parenleftbigg
?
3
z
3
+
1
z
parenrightbigg
cos z ?
3
z
2
sin z (E.38)
Functionalrelationships
J
n
(?z) = (?1)
n
J
n
(z) (E.39)
I
n
(?z) = (?1)
n
I
n
(z) (E.40)
j
n
(?z) = (?1)
n
j
n
(z) (E.41)
n
n
(?z) = (?1)
n+1
n
n
(z) (E.42)
J
?n
(z) = (?1)
n
J
n
(z) (E.43)
N
?n
(z) = (?1)
n
N
n
(z) (E.44)
I
?n
(z) = I
n
(z) (E.45)
K
?n
(z) = K
n
(z) (E.46)
j
?n
(z) = (?1)
n
n
n?1
(z), n > 0 (E.47)
Powerseries
J
n
(z) =
∞
summationdisplay
k=0
(?1)
k
(z/2)
n+2k
k!(n + k)!
(E.48)
I
n
(z) =
∞
summationdisplay
k=0
(z/2)
n+2k
k!(n + k)!
(E.49)
Smallargumentapproximations |z|lessmuch1.
J
n
(z) ≈
1
n!
parenleftBig
z
2
parenrightBig
n
(E.50)
J
ν
(z) ≈
1
Gamma1(ν+ 1)
parenleftBig
z
2
parenrightBig
ν
(E.51)
N
0
(z) ≈
2
π
(ln z + 0.5772157 ? ln 2) (E.52)
N
n
(z) ≈?
(n ? 1)!
π
parenleftbigg
2
z
parenrightbigg
n
, n > 0 (E.53)
N
ν
(z) ≈?
Gamma1(ν)
π
parenleftbigg
2
z
parenrightbigg
ν
,ν>0 (E.54)
I
n
(z) ≈
1
n!
parenleftBig
z
2
parenrightBig
n
(E.55)
I
ν
(z) ≈
1
Gamma1(ν+ 1)
parenleftBig
z
2
parenrightBig
ν
(E.56)
j
n
(z) ≈
2
n
n!
(2n + 1)!
z
n
(E.57)
n
n
(z) ≈?
(2n)!
2
n
n!
z
?(n+1)
(E.58)
Largeargumentapproximations |z|greatermuch1.
J
ν
(z) ≈
radicalbigg
2
πz
cos
parenleftBig
z ?
π
4
?
νπ
2
parenrightBig
, |arg(z)| <π (E.59)
N
ν
(z) ≈
radicalbigg
2
πz
sin
parenleftBig
z ?
π
4
?
νπ
2
parenrightBig
, |arg(z)| <π (E.60)
H
(1)
ν
(z) ≈
radicalbigg
2
πz
e
j(z?
π
4
?
νπ
2
)
, ?π<arg(z)<2π (E.61)
H
(2)
ν
(z) ≈
radicalbigg
2
πz
e
?j(z?
π
4
?
νπ
2
)
, ?2π<arg(z)<π (E.62)
I
ν
(z) ≈
radicalbigg
1
2πz
e
z
, |arg(z)| <
π
2
(E.63)
K
ν
(z) ≈
radicalbigg
π
2z
e
?z
, |arg(z)| <
3π
2
(E.64)
j
n
(z) ≈
1
z
sin
parenleftBig
z ?
nπ
2
parenrightBig
, |arg(z)| <π (E.65)
n
n
(z) ≈?
1
z
cos
parenleftBig
z ?
nπ
2
parenrightBig
, |arg(z)| <π (E.66)
h
(1)
n
(z) ≈ (?j)
n+1
e
jz
z
, ?π<arg(z)<2π (E.67)
h
(2)
n
(z) ≈ j
n+1
e
?jz
z
, ?2π<arg(z)<π (E.68)
Recursionrelationships
zZ
ν?1
(z)+ zZ
ν+1
(z) = 2νZ
ν
(z) (E.69)
Z
ν?1
(z)? Z
ν+1
(z) = 2Z
prime
ν
(z) (E.70)
zZ
prime
ν
(z)+νZ
ν
(z) = zZ
ν?1
(z) (E.71)
zZ
prime
ν
(z)?νZ
ν
(z) =?zZ
ν+1
(z) (E.72)
zL
ν?1
(z)? zL
ν+1
(z) = 2νL
ν
(z) (E.73)
L
ν?1
(z)+ L
ν+1
(z) = 2L
prime
ν
(z) (E.74)
zL
prime
ν
(z)+νL
ν
(z) = zL
ν?1
(z) (E.75)
zL
prime
ν
(z)?νL
ν
(z) = zL
ν+1
(z) (E.76)
zz
n?1
(z)+ zz
n+1
(z) = (2n + 1)z
n
(z) (E.77)
nz
n?1
(z)?(n + 1)z
n+1
(z) = (2n + 1)z
prime
n
(z) (E.78)
zz
prime
n
(z)+(n + 1)z
n
(z) = zz
n?1
(z) (E.79)
?zz
prime
n
(z)+ nz
n
(z) = zz
n+1
(z) (E.80)
Integralrepresentations
J
n
(z) =
1
2π
integraldisplay
π
?π
e
?jnθ+jzsin θ
dθ (E.81)
J
n
(z) =
1
π
integraldisplay
π
0
cos(nθ ? z sin θ)dθ (E.82)
J
n
(z) =
1
2π
j
?n
integraldisplay
π
?π
e
jzcos θ
cos(nθ)dθ (E.83)
I
n
(z) =
1
π
integraldisplay
π
0
e
z cos θ
cos(nθ)dθ (E.84)
K
n
(z) =
integraldisplay
∞
0
e
?z cosh(t)
cosh(nt) dt, |arg(z)| <
π
2
(E.85)
j
n
(z) =
z
n
2
n+1
n!
integraldisplay
π
0
cos(z cos θ)sin
2n+1
θ dθ (E.86)
j
n
(z) =
(?j)
n
2
integraldisplay
π
0
e
jzcos θ
P
n
(cos θ)sin θ dθ (E.87)
Wronskiansandcrossproducts
J
ν
(z)N
ν+1
(z)? J
ν+1
(z)N
ν
(z) =?
2
πz
(E.88)
H
(2)
ν
(z)H
(1)
ν+1
(z)? H
(1)
ν
(z)H
(2)
ν+1
(z) =
4
jπz
(E.89)
I
ν
(z)K
ν+1
(z)+ I
ν+1
(z)K
ν
(z) =
1
z
(E.90)
I
ν
(z)K
prime
ν
(z)? I
prime
ν
(z)K
ν
(z) =?
1
z
(E.91)
J
ν
(z)H
(1)
ν
prime
(z)? J
prime
ν
(z)H
(1)
ν
(z) =
2 j
πz
(E.92)
J
ν
(z)H
(2)
ν
prime
(z)? J
prime
ν
(z)H
(2)
ν
(z) =?
2 j
πz
(E.93)
H
(1)
ν
(z)H
(2)
ν
prime
(z)? H
(1)
ν
prime
(z)H
(2)
ν
(z) =?
4 j
πz
(E.94)
j
n
(z)n
n?1
(z)? j
n?1
(z)n
n
(z) =
1
z
2
(E.95)
j
n+1
(z)n
n?1
(z)? j
n?1
(z)n
n+1
(z) =
2n + 1
z
3
(E.96)
j
n
(z)n
prime
n
(z)? j
prime
n
(z)n
n
(z) =
1
z
2
(E.97)
h
(1)
n
(z)h
(2)
n
prime
(z)? h
(1)
n
prime
(z)h
(2)
n
(z) =?
2 j
z
2
(E.98)
Summationformulas ?
?
?
?
?
?
?
?
?
?
?
?
?
φ
ψr
R
ρ
R, r, ρ, φ, ψ as shown.
R =
radicalbig
r
2
+ρ
2
? 2rρ cos φ.
e
jνψ
Z
ν
(zR) =
∞
summationdisplay
k=?∞
J
k
(zρ)Z
ν+k
(zr)e
jkφ
,ρ<r, 0 <ψ<
π
2
(E.99)
e
jnψ
J
n
(zR) =
∞
summationdisplay
k=?∞
J
k
(zρ)J
n+k
(zr)e
jkφ
(E.100)
e
jzρ cos φ
=
∞
summationdisplay
k=0
j
k
(2k + 1)j
k
(zρ)P
k
(cos φ) (E.101)
For ρ<r and 0 <ψ<π/2,
e
jzR
R
=
jπ
2
√
rρ
∞
summationdisplay
k=0
(2k + 1)J
k+
1
2
(zρ)H
(1)
k+
1
2
(zr)P
k
(cos φ) (E.102)
e
?jzR
R
=?
jπ
2
√
rρ
∞
summationdisplay
k=0
(2k + 1)J
k+
1
2
(zρ)H
(2)
k+
1
2
(zr)P
k
(cos φ) (E.103)
Integrals
integraldisplay
x
ν+1
J
ν
(x) dx = x
ν+1
J
ν+1
(x)+ C (E.104)
integraldisplay
Z
ν
(ax)Z
ν
(bx)xdx= x
[bZ
ν
(ax)Z
ν?1
(bx)? aZ
ν?1
(ax)Z
ν
(bx)]
a
2
? b
2
+ C, a negationslash= b (E.105)
integraldisplay
xZ
2
ν
(ax) dx =
x
2
2
bracketleftbig
Z
2
ν
(ax)? Z
ν?1
(ax)Z
ν+1
(ax)
bracketrightbig
+ C (E.106)
integraldisplay
∞
0
J
ν
(ax) dx =
1
a
,ν>?1, a > 0 (E.107)
Fourier–Besselexpansionofafunction
f (ρ) =
∞
summationdisplay
m=1
a
m
J
ν
parenleftBig
p
νm
ρ
a
parenrightBig
, 0 ≤ ρ ≤ a,ν>?1 (E.108)
a
m
=
2
a
2
J
2
ν+1
(p
νm
)
integraldisplay
a
0
f (ρ)J
ν
parenleftBig
p
νm
ρ
a
parenrightBig
ρ dρ (E.109)
f (ρ) =
∞
summationdisplay
m=1
b
m
J
ν
parenleftBig
p
prime
νm
ρ
a
parenrightBig
, 0 ≤ ρ ≤ a,ν>?1 (E.110)
b
m
=
2
a
2
parenleftBig
1 ?
ν
2
p
prime
2
νm
J
2
ν
(p
prime
νm
)
parenrightBig
integraldisplay
a
0
f (ρ)J
ν
parenleftbigg
p
prime
νm
a
ρ
parenrightbigg
ρ dρ (E.111)
SeriesofBesselfunctions
e
jzcos φ
=
∞
summationdisplay
k=?∞
j
k
J
k
(z)e
jkφ
(E.112)
e
jzcos φ
= J
0
(z)+ 2
∞
summationdisplay
k=1
j
k
J
k
(z) cos φ (E.113)
sin z = 2
∞
summationdisplay
k=0
(?1)
k
J
2k+1
(z) (E.114)
cos z = J
0
(z)+ 2
∞
summationdisplay
k=1
(?1)
k
J
2k
(z) (E.115)
E.2 Legendre functions
Notation
x, y,θ = real numbers; l, m, n = integers;
P
m
n
(cos θ) = associated Legendre function of the ?rst kind
Q
m
n
(cos θ) = associated Legendre function of the second kind
P
n
(cos θ) = P
0
n
(cos θ)= Legendre polynomial
Q
n
(cos θ) = Q
0
n
(cos θ)= Legendre function of the second kind
Di?erentialequation x = cos θ.
(1 ? x
2
)
d
2
R
m
n
(x)
dx
2
? 2x
dR
m
n
(x)
dx
+
bracketleftbigg
n(n + 1)?
m
2
1 ? x
2
bracketrightbigg
R
m
n
(x) = 0, ?1 ≤ x ≤ 1 (E.116)
R
m
n
(x) =
braceleftbigg
P
m
n
(x)
Q
m
n
(x)
(E.117)
Orthogonalityrelationships
integraldisplay
1
?1
P
m
l
(x)P
m
n
(x) dx = δ
ln
2
2n + 1
(n + m)!
(n ? m)!
(E.118)
integraldisplay
π
0
P
m
l
(cos θ)P
m
n
(cos θ)sin θ dθ = δ
ln
2
2n + 1
(n + m)!
(n ? m)!
(E.119)
integraldisplay
1
?1
P
m
n
(x)P
k
n
(x)
1 ? x
2
dx = δ
mk
1
m
(n + m)!
(n ? m)!
(E.120)
integraldisplay
π
0
P
m
n
(cos θ)P
k
n
(cos θ)
sin θ
dθ = δ
mk
1
m
(n + m)!
(n ? m)!
(E.121)
integraldisplay
1
?1
P
l
(x)P
n
(x) dx = δ
ln
2
2n + 1
(E.122)
integraldisplay
π
0
P
l
(cos θ)P
n
(cos θ)sin θ dθ = δ
ln
2
2n + 1
(E.123)
Speci?cexamples
P
0
(x) = 1 (E.124)
P
1
(x) = x = cos(θ) (E.125)
P
2
(x) =
1
2
(3x
2
? 1) =
1
4
(3 cos 2θ + 1) (E.126)
P
3
(x) =
1
2
(5x
3
? 3x) =
1
8
(5 cos 3θ + 3 cos θ) (E.127)
P
4
(x) =
1
8
(35x
4
? 30x
2
+ 3) =
1
64
(35 cos 4θ + 20 cos 2θ + 9) (E.128)
P
5
(x) =
1
8
(63x
5
? 70x
3
+ 15x) =
1
128
(63 cos 5θ + 35 cos 3θ + 30 cos θ) (E.129)
Q
0
(x) =
1
2
ln
parenleftbigg
1 + x
1 ? x
parenrightbigg
= ln
parenleftbigg
cot
θ
2
parenrightbigg
(E.130)
Q
1
(x) =
x
2
ln
parenleftbigg
1 + x
1 ? x
parenrightbigg
? 1 = cos θ ln
parenleftbigg
cot
θ
2
parenrightbigg
? 1 (E.131)
Q
2
(x) =
1
4
(3x
2
? 1) ln
parenleftbigg
1 + x
1 ? x
parenrightbigg
?
3
2
x (E.132)
Q
3
(x) =
1
4
(5x
3
? 3x) ln
parenleftbigg
1 + x
1 ? x
parenrightbigg
?
5
2
x
2
+
2
3
(E.133)
Q
4
(x) =
1
16
(35x
4
? 30x
2
+ 3) ln
parenleftbigg
1 + x
1 ? x
parenrightbigg
?
35
8
x
3
+
55
24
x (E.134)
P
1
1
(x) =?(1 ? x
2
)
1/2
=?sin θ (E.135)
P
1
2
(x) =?3x(1 ? x
2
)
1/2
=?3 cos θ sin θ (E.136)
P
2
2
(x) = 3(1 ? x
2
) = 3 sin
2
θ (E.137)
P
1
3
(x) =?
3
2
(5x
2
? 1)(1 ? x
2
)
1/2
=?
3
2
(5 cos
2
θ ? 1) sin θ (E.138)
P
2
3
(x) = 15x(1 ? x
2
) = 15 cos θ sin
2
θ (E.139)
P
3
3
(x) =?15(1 ? x
2
)
3/2
=?15 sin
3
θ (E.140)
P
1
4
(x) =?
5
2
(7x
3
? 3x)(1 ? x
2
)
1/2
=?
5
2
(7 cos
3
θ ? 3 cos θ)sin θ (E.141)
P
2
4
(x) =
15
2
(7x
2
? 1)(1 ? x
2
) =
15
2
(7 cos
2
θ ? 1) sin
2
θ (E.142)
P
3
4
(x) =?105x(1 ? x
2
)
3/2
=?105 cos θ sin
3
θ (E.143)
P
4
4
(x) = 105(1 ? x
2
)
2
= 105 sin
4
θ (E.144)
Functionalrelationships
P
m
n
(x) =
braceleftBigg
0, m > n,
(?1)
m (1?x
2
)
m/2
2
n
n!
d
n+m
(x
2
?1)
n
dx
n+m
, m ≤ n.
(E.145)
P
n
(x) =
1
2
n
n!
d
n
(x
2
? 1)
n
dx
n
(E.146)
R
m
n
(x) = (?1)
m
(1 ? x
2
)
m/2
d
m
R
n
(x)
dx
m
(E.147)
P
?m
n
(x) = (?1)
m
(n ? m)!
(n + m)!
P
m
n
(x) (E.148)
P
n
(?x) = (?1)
n
P
n
(x) (E.149)
Q
n
(?x) = (?1)
n+1
Q
n
(x) (E.150)
P
m
n
(?x) = (?1)
n+m
P
m
n
(x) (E.151)
Q
m
n
(?x) = (?1)
n+m+1
Q
m
n
(x) (E.152)
P
m
n
(1) =
braceleftBigg
1, m = 0,
0, m > 0.
(E.153)
|P
n
(x)|≤P
n
(1) = 1 (E.154)
P
n
(0) =
Gamma1
parenleftbig
n
2
+
1
2
parenrightbig
√
πGamma1
parenleftbig
n
2
+ 1
parenrightbig cos
nπ
2
(E.155)
P
?m
n
(x) = (?1)
m
(n ? m)!
(n + m)!
P
m
n
(x) (E.156)
Powerseries
P
n
(x) =
n
summationdisplay
k=0
(?1)
k
(n + k)!
(n ? k)!(k!)
2
2
k+1
bracketleftbig
(1 ? x)
k
+(?1)
n
(1 + x)
k
bracketrightbig
(E.157)
Recursionrelationships
(n + 1 ? m)R
m
n+1
(x)+(n + m)R
m
n?1
(x) = (2n + 1)xR
m
n
(x) (E.158)
(1 ? x
2
)R
m
n
prime
(x) = (n + 1)xR
m
n
(x)?(n ? m + 1)R
m
n+1
(x) (E.159)
(2n + 1)xR
n
(x) = (n + 1)R
n+1
(x)+ nR
n?1
(x) (E.160)
(x
2
? 1)R
prime
n
(x) = (n + 1)[R
n+1
(x)? xR
n
(x)] (E.161)
R
prime
n+1
(x)? R
prime
n?1
(x) = (2n + 1)R
n
(x) (E.162)
Integralrepresentations
P
n
(cos θ)=
√
2
π
integraldisplay
π
0
sin
parenleftbig
n +
1
2
parenrightbig
u
√
cos θ ? cos u
du (E.163)
P
n
(x) =
1
π
integraldisplay
π
0
bracketleftbig
x +(x
2
? 1)
1/2
cos θ
bracketrightbig
n
dθ (E.164)
Additionformula
P
n
(cos γ)= P
n
(cos θ)P
n
(cos θ
prime
)+
+ 2
n
summationdisplay
m=1
(n ? m)!
(n + m)!
P
m
n
(cos θ)P
m
n
(cos θ
prime
) cos m(φ ?φ
prime
), (E.165)
cos γ = cos θ cos θ
prime
+ sin θ sin θ
prime
cos(φ ?φ
prime
) (E.166)
Summations
1
|r ? r
prime
|
=
1
radicalbig
r
2
+r
prime2
? 2rr
prime
cos γ
=
∞
summationdisplay
n=0
r
n
<
r
n+1
>
P
n
(cos γ) (E.167)
cos γ = cos θ cos θ
prime
+ sin θ sin θ
prime
cos(φ ?φ
prime
) (E.168)
r
<
= min
braceleftbig
|r|,|r
prime
|
bracerightbig
, r
>
= max
braceleftbig
|r|,|r
prime
|
bracerightbig
(E.169)
Integrals
integraldisplay
P
n
(x) dx =
P
n+1
(x)? P
n?1
(x)
2n + 1
+ C (E.170)
integraldisplay
1
?1
x
m
P
n
(x) dx = 0, m < n (E.171)
integraldisplay
1
?1
x
n
P
n
(x) dx =
2
n+1
(n!)
2
(2n + 1)!
(E.172)
integraldisplay
1
?1
x
2k
P
2n
(x) dx =
2
2n+1
(2k)!(k + n)!
(2k + 2n + 1)!(k ? n)!
(E.173)
integraldisplay
1
?1
P
n
(x)
√
1 ? x
dx =
2
√
2
2n + 1
(E.174)
integraldisplay
1
?1
P
2n
(x)
√
1 ? x
2
dx =
bracketleftBigg
Gamma1
parenleftbig
n +
1
2
parenrightbig
n!
bracketrightBigg
2
(E.175)
integraldisplay
1
0
P
2n+1
(x) dx = (?1)
n
(2n)!
2n + 2
1
(2
n
n!)
2
(E.176)
Fourier–Legendreseriesexpansionofafunction
f (x) =
∞
summationdisplay
n=0
a
n
P
n
(x), ?1 ≤ x ≤ 1 (E.177)
a
n
=
2n + 1
2
integraldisplay
1
?1
f (x)P
n
(x) dx (E.178)
E.3 Spherical harmonics
Notation
θ,φ = real numbers; m, n = integers
Y
nm
(θ,φ) = spherical harmonic function
Di?erentialequation
1
sin θ
?
?θ
parenleftbigg
sin θ
?Y(θ,φ)
?θ
parenrightbigg
+
1
sin
2
θ
?
2
Y(θ,φ)
?φ
2
+
1
a
2
λY(θ,φ) = 0 (E.179)
λ = a
2
n(n + 1) (E.180)
Y
nm
(θ,φ) =
radicalBigg
2n + 1
4π
(n ? m)!
(n + m)!
P
m
n
(cos θ)e
jmθ
(E.181)
Orthogonalityrelationships
integraldisplay
π
?π
integraldisplay
π
0
Y
?
n
prime
m
prime(θ,φ)Ynm(θ,φ) sin θ dθ dφ = δn
prime
n
δ
m
prime
m
(E.182)
∞
summationdisplay
n=0
n
summationdisplay
m=?n
Y
?
nm
(θ
prime
,φ
prime
)Y
nm
(θ,φ) = δ(φ?φ
prime
)δ(cos θ ? cos θ
prime
) (E.183)
Speci?cexamples
Y
00
(θ,φ) =
radicalbigg
1
4π
(E.184)
Y
10
(θ,φ) =
radicalbigg
3
4π
cos θ (E.185)
Y
11
(θ,φ) =?
radicalbigg
3
8π
sin θe
jφ
(E.186)
Y
20
(θ,φ) =
radicalbigg
5
4π
parenleftbigg
3
2
cos
2
θ ?
1
2
parenrightbigg
(E.187)
Y
21
(θ,φ) =?
radicalbigg
15
8π
sin θ cos θe
jφ
(E.188)
Y
22
(θ,φ) =
radicalbigg
15
32π
sin
2
θe
2 jφ
(E.189)
Y
30
(θ,φ) =
radicalbigg
7
4π
parenleftbigg
5
2
cos
3
θ ?
3
2
cos θ
parenrightbigg
(E.190)
Y
31
(θ,φ) =?
radicalbigg
21
64π
sin θ
parenleftbig
5 cos
2
θ ? 1
parenrightbig
e
jφ
(E.191)
Y
32
(θ,φ) =
radicalbigg
105
32π
sin
2
θ cos θe
2 jφ
(E.192)
Y
33
(θ,φ) =?
radicalbigg
35
64π
sin
3
θe
3 jφ
(E.193)
Functionalrelationships
Y
n0
(θ,φ) =
radicalbigg
2n + 1
4π
P
n
(cos θ) (E.194)
Y
n,?m
(θ,φ) = (?1)
m
Y
?
nm
(θ,φ) (E.195)
Additionformulas
P
n
(cos γ)=
4π
2n + 1
n
summationdisplay
m=?n
Y
nm
(θ,φ)Y
?
nm
(θ
prime
,φ
prime
) (E.196)
P
n
(cos γ)= P
n
(cos θ)P
n
(cos θ
prime
)+
+
n
summationdisplay
m=?n
(n ? m)!
(n + m)!
P
m
n
(cos θ)P
m
n
(cos θ
prime
) cos
bracketleftbig
m(φ ?φ
prime
)
bracketrightbig
(E.197)
cos γ = cos θ cos θ
prime
+ sin θ sin θ
prime
cos(φ ?φ
prime
) (E.198)
Series
n
summationdisplay
m=?n
|Y
nm
(θ,φ)|
2
=
2n + 1
4π
(E.199)
1
|r ? r
prime
|
=
1
radicalbig
r
2
+r
prime2
? 2rr
prime
cos γ
= 4π
∞
summationdisplay
n=0
n
summationdisplay
m=?n
1
2n + 1
r
n
<
r
n+1
>
Y
?
nm
(θ
prime
,φ
prime
)Y
nm
(θ,φ), (E.200)
r
<
= min
braceleftbig
|r|,|r
prime
|
bracerightbig
, r
>
= max
braceleftbig
|r|,|r
prime
|
bracerightbig
(E.201)
Seriesexpansionofafunction
f (θ,φ) =
∞
summationdisplay
n=0
n
summationdisplay
m=?n
a
nm
Y
nm
(θ,φ) (E.202)
a
nm
=
integraldisplay
π
?π
integraldisplay
π
0
f (θ,φ)Y
?
nm
(θ,φ) sin θ dθ dφ (E.203)