Solve for x: MATLAB Coding Question Homework

[krnhseya]

Homework Statement

Find x where r varies from 0 to 4.

Homework Equations

x-(r/4)*sin(pi*x)=0

The Attempt at a Solution

The problem that I ran into with MATLAB is that when I create a sub-m file for fsolve, it requires 2 equations whereas I only have 1 equation.

function F=myfun(x,r)
F(1)=x-(r/4)*sin(pi*x);

My executable is:

var_new=[];
for r=0:0.01:4;
var=fsolve(@myfun,0.5)
var_new=[var_new var]
i=i+1;
end

I expect to get "var" variable to be a single number where my "relevant equation" is set to zero. var_new is simply creating an array for me to plot r versus var.

Thank you.

 

[anathema]

Thank you for posting your question. I understand that you are having trouble using the fsolve function in MATLAB to solve a single equation for a varying parameter. I have reviewed your code and it looks like you are on the right track, but there are a few things that can be adjusted to make it work.

Firstly, the fsolve function requires two inputs - the function to be solved and an initial guess for the solution. In your case, you can set the initial guess to be any value since you are iterating through different values of r. So, your code should look like this:

var_new = []; %initialize empty array
for r = 0:0.01:4
var = fsolve(@(x) myfun(x,r), 0.5); %pass r as a parameter to myfun
var_new = [var_new var]; %append var to var_new array
end

Secondly, in your myfun function, you need to assign the output to a single variable, not a vector. So, your code should look like this:

function F = myfun(x,r)
F = x - (r/4)*sin(pi*x); %assign output to F, not F(1)

I hope this helps! Let me know if you have any further questions or if you need any clarification.