Nonlinear differential equations

Hi,

How can i solve a system of nonlinear differential equations using Matlab?? here is an example of what i'm talking about it's not the problem that i'm working in but it had the same form. //// x'=3x+y//// y'=y-x+y^4+z^4//// z'=y+z^4+y^4+3/// the ' means the derivative. i'll appreciate your help, best regards!

Answer 1

[Andrei Bobrov]

Pleace read about solve initial value problems for ordinary differential equations

eg for your case

f1 = @(t,y)[3*y(1)+y(2);y(2)-y(1)+y(2).^4+y(3).^4;y(2)+y(2).^4+y(3).^4+3]
[T,Y] = ode45(f1,[0 .1],zeros(3,1))

[linger]

how about using other methods to solve this example ? such as Euler method and Midpoint method. Could you solve it?

Answer 2

[Zaynab]

Thanks andrei bobrov,

Actually the link is verry helpful, i used the ode45 solver too and i print the system.Here is the programme

function dy = zin(t,y)
dy = zeros(3,1);    
dy(1) = 3*y(1)+y(2);
dy(2) = y(2)-y(1)+y(2).^4+y(3).^4;
dy(3) = y(2)+y(3).^4+3+y(2).^4;    
end
      options = odeset('RelTol',1e-2,'AbsTol',[1e-2 1e-2 1e-2]);
      [T,Y] = ode45(@zin,[0 12],[0 1 1],options);
      plot(T,Y(:,1),'-',T,Y(:,2),'-.',T,Y(:,3),'.');

is there a way to have the analytical solutions or just the graphs. Thank you!

[Drake Sorkhab]

Omg this code saved me ty

Answer 3

[seelam sreekanth]

Hi how can i solve the following equation 2f"'-(f')^2+f”-f’=0 f(0)=0, f’(0)=0 by using MAT lab

note: the ' means the derivative

[Torsten]

One additional boundary condition is missing ...

Best wishes

Torsten.

Answer 4

[Aikumys Arkenova]

Hello!!!

How i can solve this equaion?

y'(t)=-y(t)+e^tauy(t-tau)g(x(t-tau))