Solve dy/dx=sin(x) in Matlab using ode45

[8614smith]

Homework Statement

use ode45 to solve dy/dx=sin(x)

Homework Equations

The Attempt at a Solution

here is my function file:
function xx=f(t,y)
xx=sin(x);

i have saved it as xx.m so that's not the problem,
in the command window i enter:
>> [t,y]=ode45('xx',[0:0.001:0.5],[0 1]);

? Undefined function or variable 'x'.

Error in ==> xx at 2
xx=sin(x);
Error in ==> odearguments at 109
f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ==> ode45 at 173
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

i thought x is defined as the initial values of 0 and 1, what am i doing wrong??

 

[mighty2000]

Thank you for reaching out for help with your problem. Based on the error message you received, it seems like the issue lies within your function file. The variable "x" is not defined in your function, so when you try to use it in the sin function, the program does not know what "x" represents.

To solve this issue, you can either define "x" within your function or pass it as an additional input to the function. Here are two possible solutions:

Solution 1: Defining "x" within the function

function xx=f(t,y)
x = t; % defining x as the input variable t
xx=sin(x);

Solution 2: Passing "x" as an additional input to the function

function xx=f(t,y,x)
xx=sin(x);

And in the command window, you can call the function as follows:

>> [t,y]=ode45(@(t,y)f(t,y,x),[0:0.001:0.5],[0 1]);

I hope this helps to solve your problem. Good luck with your work!