How to solve Two coupled ODE problem

hello all,

actually, i have some problem about to solve two coupled ODE that are dependent on each other. if u all have time can u give me some guide about to coding with two coupled equations problem below and plot the graph :-

   function dydt = odefun1(t,y,Aq,Bq,Cq,Ay,By,Cy)

A=1;
B=2;
C=1;
D=3;
E=1;
F=1;
h=1;    

Aq=y(1);
Bq=y(2);
Ay=y(3);
By=y(4);

dydt = zeros(4,1);

dydt(1) = F*dydt(2)-D*Bq-E*Aq;
dydt(2) = (C*Aq-B*By-h*Ay)/A;

dydt = [dydt(1) ; dydt(2) ];

t_start = 0;
t_end   = 10;  %final time in seconds.
%time_span =[ t_start t_end];
time_span =t_start:0.09:t_end;

initial_position = 0;
initial_speed    = 0;
x0 = [initial_position  initial_speed];

[t,y]=ode45(@odefun1,time_span,x0);
    plot(t,y(:,1));
    hold on;
    plot(t,y(:,2));

end

hope u all can answer this question.. thank you in advance. best regards, azam

[James Tursa]

If y is a 4-element vector, why are you building a dydt vector that has only 2 elements? If dydt(1) depends on dydt(2), why aren't you calculating dydt(2) before you calculate dydt(1)?

[Azam Axel]

Thank you James for your answer,but i'm still having the same problem though. i changed my code as shown below. no error but cannot produce the graph instead. can u guide me with example code. very appreciate if u can answer this.. tq

 function dydt = odefun1(t,y,Aq,Bq,Cq,Ay,By,Cy)
  A=1;
  B=2;
  C=1;
  D=3;
  E=1;
  F=1;
  h=1;  

Aq=y(1);
Bq=y(2);
Ay=y(3);
By=y(4);

dydt = zeros(4,1);

dydt(1) = (C*Aq-B*By-h*Ay)/A;
dydt(2) = F*dydt(1)-D*Bq-E*Aq;

t_start = 0;
t_end   = 10;  %final time in seconds.

 %time_span =[ t_start t_end];
  time_span =t_start:0.09:t_end;

initial_position = 0;
initial_speed    = 0;

x0 = [initial_position  initial_speed];

[t,y]=ode45(@odefun1,time_span,x0);
    plot(t,y(:,1));
    hold on;

    end

Answer 1

[PUJARI MURAGA]

I have solution for you.

Did you got ?

[Azam Axel]

can you share with me what you got.. tq in advance pujari 4 answer this question..