Plotting the ODE without an analytical solution

Question

Joo Seo Lee 2020-5-25

回答： Steven Lord 2020-5-25

How do I plot the equation

d^2(x)/dt^2=0.002cos(x-t)-sin(x)

where x(0)=0.2 and x'(0)=0 for t=0:100?

I asked the question before, but the graph that was plotted was starting from x(0)=0

the answer I got before was

dfun = @(t, x) [x(2); 0.002*cos(x(1)-t)-sin(x(1))];

time = [0 100];

ic = [0; 0];

[t, x] = ode15s(dfun, time, ic);

plot(t, x);

legend({'x', 'xdot'})

Answer 1

Steven Lord 2020-5-25

If your initial conditions are supposed to be: "where x(0)=0.2 and x'(0)=0 for t=0:100?" why are you specifying them as x(0) = 0 and x'(0) = 0?

ic = [0; 0];

Instead specify your desired initial conditions.

ic = [0.2; 0];