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MATHEMATICAL EQUATIONS
47-43
Series Containing Bessel Functions:
exp(-ju situ)
=
2
JJU)
exp
(-jnx)
X
n=-m
m
cos@
cosx)
=
J&)
+
22
(-l)nJ&)
cos2nx
n=l
X
cos(2n
-
l)x
Orthogonal Polynomials
Any set of polynomials
cf,(x)}
with the property
6
w(x)~(x)f~(x)d~
=
0,
for
rn
z
n
=
h,, for
rn
=
n
is called a set of orthogonal polynomials on the interval
(a,
b)
with respect to the weight function
w(x).
These
functions occur in the Gauss quadrature equations
among other places. Chebishev polynomials are in-
volved in the theory of the Chebishev filter; Hermite
polynomials arise in the refinements
of
the central limit
theorem, the so-called Edgeworth series, etc. The
important properties are summarized in Table
1.
NUMERICAL ANALYSIS
Algorithms for Solving
F(x)
=
0
Bisection Method and Regula
Falsi
(Rule
of
False
Position): First determine
x,
and
x2
such that
F(x1)F(x2)
<
0,
Le.,
xl
and
x2
are points at which the
function has opposite signs.
Bisection Method: Calculate
x3
=
(x,
+
x,)/2
Regula Falsi: Calculate
To obtain the next approximation, take
x3
and
xi,
i
=
1
or
2,
such that
F(x3)F(xi)
<
0,
and repeat the
procedure.
Newton-Raphson: Take some initial value
xl
and
calculate successively
xn+l
=
xn
-
[F(x,)/F'(x,)],
n
=
1,
2,
3
*
.
This method may not converge. When it converges,
the rate
of
convergence is generally faster than the
bisection method or the regula falsi.
Algorithm for Solving
Fk
Y)
=
G(x,
Y)
=
0
The following is an extension of the Newton-
Raphson method described above. Take some initial
values
xI
and
yl
and calculate successively
TABLE
1.
PROPERTIES
OF
ORTHOGONAL POLYNOMIALS
e
-9
H,(x)
Hermite
--co
t,(x)
Laguerre
0
-co
e
-'
P,,(x)
Legendre
-
1
1
I
1
*
[n/2]
denotes
the
largest integer
less
than
or
equal
to
n/2.