The code after the semi-colon in this line of code seems to be a typo
opts = odeset('RelTol',1e-6,'AbsTol',1e-8);function [dXdt] = Problem02ODEFunction(t,X)
After removing it, the code works and the plots are there -
%x1'=-3x1-200x2
%x2'=200x1-3x2
opts = odeset('RelTol',1e-6,'AbsTol',1e-8);
soln = ode45(@Problem02ODEFunction,[0 1],[-10 10],opts)
figure;
plot(soln.x,soln.y(1,:),'-','linewidth',0.5);
hold on;
plot(soln.x,soln.y(2,:),'-','linewidth',0.5);
grid on;
title('Problem 2 ODE45 Solution');
xlabel('Time (s)');
ylabel('Solution');
legend('x_{1}(t)','x_{2}(t)','location','best');
function dXdt = Problem02ODEFunction(t,X)
x1 = X(1);
x2 = X(2);
dx1dt = -3*x1 - 200*x2;
dx2dt = 200*x1 - 3*x2;
[dXdt] = [dx1dt; dx2dt];
end
