Using the Lagrange’s interpolation formula, function f ( ) x can be
expressed as[1]
( ) ( )
j j
n
j
f x ∑l x f
=
=
0
(1)
where
j
f stands for ( )
j
f x , while l (x)
j
is as given below
( )
( )
( ) ( )
l x
x
x x x
j
j j
=
− ′
π
π
. (2)
In the above equation (2), prime denotes differentiation with respect to x and
( ) ( )( ) ( ) n
x = x − x x − x . . . . x − x π 0 1
. (3)