%% in dsolve you just need to plot the solution with the time, for example:
syms theta(t)
sol = dsolve(...)
t= 0:1:40;
plot(t, sol)
but the given equation contain sin(theta) so there is no analytic solution for it, so dsolve isnt appropriated here
%% in the ode45 function there is a paramether for time, for example:
tspan = 0:1:40;
init = [1 0];
[t,y] = ode45(@pendulum, tspan, init);
plot(t,y)
