![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/965510/image.png)
Solving 2nd Order Differential Equation Symbolically
80 visualizaciones (últimos 30 días)
Mostrar comentarios más antiguos
Jordan Stanley
el 15 de Abr. de 2022
Editada: Jordan Stanley
el 16 de Abr. de 2022
Hello,
I have the 2nd order differential equation: y'' + 2y' + y = 0 with the initial conditions y(-1) = 0, y'(0) = 0.
I need to solve this equation symbolically and graph the solution.
Here is what I have so far...
syms y(x)
Dy = diff(y);
D2y = diff(y,2);
ode = D2y + 2*Dy + y == 0;
ySol = dsolve(ode,[y(-1)==0,Dy(0)==0])
a = linspace(0,1,20);
b = eval(vectorize(ySol));
plot(a,b)
But I get the following output.
ySol = ![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/965485/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/965485/image.png)
Error using eval
Unrecognized function or variable 'C1'.
I'd greatly appreciate any assistance.
0 comentarios
Respuesta aceptada
Star Strider
el 15 de Abr. de 2022
The
constants are the initial condition. They must be defined.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/965510/image.png)
syms y(x) y0
Dy = diff(y);
D2y = diff(y,2);
ode = D2y + 2*Dy + y == 0;
ySol(x,y0) = dsolve(ode,[Dy(0)==0,y(-1)==0,y(0)==y0])
% a = linspace(0,1,20);
% b = eval(vectorize(ySol));
figure
fsurf(ySol,[0 1 -1 1])
xlabel('x')
ylabel('y_0 (Initial Condition)')
.
16 comentarios
Torsten
el 16 de Abr. de 2022
Editada: Torsten
el 16 de Abr. de 2022
How should it be possible to solve 1. without 2. ? If you don't know the solution, you can't trace a solution curve. Or what's your opinion ?
Anyhow - I think your instructors overlooked that the equation together with its initial conditions does not only give one curve, but infinitly many. So "graphing the solution" will become difficult. But Star Strider's answer for this situation looks fine for me.
But you say you get an error. What's your code and what's the error message ?
Más respuestas (0)
Ver también
Productos
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!