Culegere de probleme de Analiz˘a numeric˘a
Culegere de probleme de Analiz˘a numeric˘a
Culegere de probleme de Analiz˘a numeric˘a
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Capitolul 6<br />
Interpolare<br />
6.1 Interpolare polinomială<br />
Fie nodurilexi ∈ [a,b], i = 0,m, i = j ⇒ xi = xj.<br />
Are loc formula <strong>de</strong> interpolare Lagrange<br />
un<strong>de</strong><br />
s¸i<br />
f = Lmf +Rmf<br />
(Lmf)(x) =<br />
m<br />
lk(x)f(xk)<br />
k=0<br />
lk(x) = (x−x0)...(x−xk−1)(x−xk+1)...(x−xm)<br />
(xk −x0)...(xk −xk−1)(xk −xk+1)...(xk −xm) =<br />
=<br />
m<br />
(x−xj)<br />
j=0<br />
j=k<br />
m<br />
=<br />
(xk −xj)<br />
j=0<br />
j=k<br />
u(x)<br />
(x−xk)u ′ (xk)<br />
un<strong>de</strong>u(x) = (x−x0)...(x−xm).<br />
Dacăα = min{x,x0,...,xm},β = max{x,x0,...,xm},f ∈ C m [α,β],f (m)<br />
<strong>de</strong>rivabilă pe(α,β)∃ξ ∈ (α,β) astfel încât<br />
(Rmf)(x) = u(x)<br />
(m+1)! f(m+1) (ξ)<br />
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