ode45 third order ode

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matlab
matlab 2020-6-22
how to solve
f''' = { [3 * f' * (f'')^2] / [(f')^2 + 1]^(5/2) + 1/f^3 - 1/f^2 + 3} * { [(f')^2 + 1]^(3/2) }
using ode45
with
f(0) = 1.1
f'(0) = 17.1
f''(0) = 144.1

采纳的回答

Ameer Hamza
Ameer Hamza 2020-6-22
Use ode45(). this ODE can be written as a system of 3 first-order ODEs
odeFun = @(t, y) [y(2);
y(3);
((3*y(2).*y(3).^2)./(y(2).^2 + 1).^(5/2) + 1./y(1).^3 - 1/y(1).^2 + 3).*((y(2).^2 + 1).^(3/2))];
tspan = [0 1];
ic = [1.1; 17.1; 144.1];
[t, y] = ode45(odeFun, tspan, ic);
plot(t, y);
However, it seems that the ODE is unstable, and the solution diverges to infinity. You may check if the equation is written correctly.

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