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Culegere de probleme de Analiz˘a numeric˘a

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Capitolul 11<br />

Rezolvarea numerică ecuat¸iilor<br />

diferent¸iale<br />

Problema 11.0.4 Aproximat¸i solut¸ia <strong>probleme</strong>i Cauchy<br />

y ′ = −y +x−1, x ∈ [0,1], y(0) = 1<br />

pentruN = 10, h = 0.1, xi = 0.1i folosind metoda lui Euler.<br />

Solut¸ie.<br />

Solut¸ia exactă este<br />

y ′ = −y +x+1, x ∈ [0,1], y(0) = 1<br />

y0 = α<br />

yi+1 = yi +hf(xi,yi)<br />

τ = h2<br />

2 y′′ (ξi)<br />

y(x) = x+e −x<br />

y0 = 1<br />

yi = yi−1 +h(−yi−1 +xi−1 +1) =<br />

= yi−1 +0·1(−yi−1 +0.1(i−1)+1) =<br />

= 0.9yi−1 +0.01(i−1)+0.1 = 0.9yi−1 +0.01i+0.09<br />

Calculele sunt date în următorul tabel<br />

xi yi y(xi) |yi −y(xi)|<br />

0.0 1.000000 1.000000 0<br />

0.1 1.000000 1.004837 0.004837<br />

0.2 1.01 1.018731 0.008731<br />

0.3 1.029 1.040818 0.011818<br />

0.4 1.0561 1.070320 0.014220<br />

164

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