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Web skærmformat. - Aarhus Universitet

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IV. Differentialligninger – 3. Generelle metoder 352<br />

I et givet punkt (Pn,tn) vil differentialet være<br />

dP = 0.08Pn(1 − Pn<br />

1000 )dt<br />

og<br />

P ≈ Pn + 0.08Pn(1 − Pn<br />

1000 )(t − tn)<br />

3.12. Eulers metode ☞ [S] 7.5 The logistic equation<br />

Eulers metode<br />

Tabellæg løsning til<br />

dP<br />

P<br />

= 0.08P(1 − ), P(0) = 100<br />

dt 1000<br />

n tn Pn<br />

1 10.0 172.0<br />

2 20.0 285.9<br />

3 30.0 449.3<br />

4 40.0 647.2<br />

5 50.0 829.9<br />

n tn Pn<br />

6 60.0 942.8<br />

7 70.0 985.9<br />

8 80.0 997.0<br />

9 90.0 999.4<br />

10 100.0 999.9<br />

3.13. Grafisk ☞ [S] 7.6 Predator-prey systems<br />

Eksempel<br />

For Lotka-Volterra systemet<br />

dR<br />

dt<br />

= kR − aRW

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