yi = f (xi). .
.
-:
Pn (x, x 0) Pn (x 0, x 1) x = x 1,
n 2. , Pn (x, x 0, x 1, x 2) n 3 ..
Pn (x, x 0, x 1, , xn- 1) n .
.
Pn (x, x 0, x 1, , xn 1) x ,
Pn (x, x 0, x 1,, xn- 1) = Pn (x 0, x 1, , xn).
Pn (x) = Pn (x 0) + (x x 0) Pn (x, x 0),
Pn (x, x 0) = Pn (x 1, x 0) + (x x 1) Pn (x, x 0, x 1)
.. Pn (x)
Pn (x) = Pn (x 0) + (x x 0) Pn (x 0, x 1) + (x x 0) (x x 1) Pn (x 0, x 1, x 2) +
+ (x x 0) (x x 1) (x xn- 1) Pn (x 0, , xn). (5.2)
(5.1) x 0, x 1, , xn. x 0, x 1, , xn , y 0, y 1, , yn , n, yi. Pn (x) f (x).
.
y = f (x). . , x , f (x) f (x) . , . f (x) g (x), f (x). g (x) .
, f (x) x 0, x 1, , xn,
yi = f (xi), i = 0, , n, g (x, a 0, a 1, , an)
g (xi, a 0, a 1, , an) = yi, i = 0, 1, , n. (5.4)
(5.4) a 0, a 1, , an, ().
g aj , . .
(5.5)
ϕ j (x) .
(5.5) (5.4). aj :
|
|
(5.6)
m = n.
, ϕ j (x)
(5.7)
, (5.7),
. ϕ j (x)
(5.5) .
x ∈[1, 1].
Tn (x) = cos[ n∙ arccos(x)]. (5.8)
, T 0(x) = 1, T 1(x) = x. n = 2
T 2(x) = cos(2arccos(x)) = cos 2 (arccos(x)) − sin2(arcos(x)) =
= 2cos 2 (arccos(x)) − 1 = −1 + 2 x 2.
Tn (x) n. , Tn 1(x), Tn (x) Tn +1(x). ,
,