Solve a second order differential equation
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Hi, I am completely new to Matlab and am looking to solve a simple second order differential equation:
y''+w^2*y=0 IC: y(0)=0, y'(0)=1 BC=[0,pi]
I am looking to solve for both y(x) and y'(x)
I understand this is a simple equation to solve and have done it fine on paper. However I have been trying different ways to solve it on matlab but to no avail. I have tried both dsolve and ode45 functions but did not quite understand what I was doing. Any help would be great. Thanks in advance, Ben
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Azzi Abdelmalek
2013-3-7
编辑：Azzi Abdelmalek
2013-3-7
% x1=y
%x2=dy
Then
%dx1=dy=x2
%dx2=d2y=-w^2*y=-w^2*x1
save this function as yourfcn
function dx=yourfcn(t,x)
w=1
dx(1)=x(2)
dx(2)=-w^2*x(1)
Then call the ode45 function
[t,x]=ode45(@yourfcn,[0,pi],[0 0])
Then deduce y
y=x(:,1)
更多回答（2 个）
Shashank Prasanna
2013-3-7
2 个投票
I really recommend going through our documentation and these things become intuitive. Most standard setup's usually have examples in the documentation:
Nicolas
2014-1-28
Hi I have written the following First the Function
function h = goo(t,y)
h = zeros(3,1);
h(1) = y(2) * y(3);
h(2) = -y(1) * y(3);
h(3) = -0.51 * y(1) * y(2);
end
and then the code
clear all
initial=[-2 -3.5 21];
time=[0 10];
[t,y] = ode45(@goo,time,initial);
plot (t,y)
However I always get the following message:
Error using feval
Undefined function 'goo' for input arguments of type 'double'.
Error in odearguments (line 88)
f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.
Error in ode45 (line 114)
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...
Can anyone help me on this Thank you
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