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Modellering i Tidsplanet

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Faltning Differensekvationer Differentialekvationer<br />

Approximation av andra-derivator<br />

Euler-approximation of första-derivata<br />

dy(t)<br />

y(nT + T ) − y(nT )<br />

dt ∣ ≈<br />

t=nT<br />

T<br />

Euler-approximation av andra-derivata<br />

=<br />

y[n + 1] − y[n]<br />

T<br />

d 2 y(t)<br />

dt 2<br />

=<br />

∣<br />

∣∣t=nT<br />

≈ dy<br />

dt | t=nT +T − dy<br />

dt | t=nT<br />

T<br />

(y[n+2]−y[n+1])/T −(y[n+1]−y[n])/T<br />

T<br />

= y[n+2]−2y[n+1]+y[n]<br />

T 2

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