MATLAB: Help with the bisection method of a certain function!

Question

Hello, I am a new user of MatLab and recently had to write up a bisection method program for the function f(x) = x + 2*cos(x).

This is what I got:

 function[f] = hw3_bisection(tol,N,a,b)
f = @(x) (x + 2*cos(x));
for counter = 1:N
    x = (a+b)/2;
    while abs(f(x)) < tol
        x = (a+b)/2;
        if f(x) == 0
           f = x;
        end
        if f(a) * f(x) > 0
            a = x;
        else
            b = x;
        end
    end
end

but the problem for me is that the output is always x + 2*cos(x), and even if I say disp(x) it gives me ans = x + 2*cos(x) and the (a+b)/2 without going through the rest of the loop. How do I fix this to get the real solution?

Answer 1

You are using 'f' for 2 different things in your function. Use a different variable for the value returned by the function.