Find roots of a first order differential equation

Hello

I have a created a function in matlab:

function [fx] = Function(x, r)

fx = r - 2*cos(x);

end

Now I would like to find the zero points of the function for r = 1 and x between - 2pi and 2pi.

Thank you!

Answer 1

[Star Strider]

Try this —

r = 1;
x = linspace(-2*pi, 2*pi, 25);
y = Function(x,r);
zxidx = find(diff(sign(y)));                                            % Indices Of Approximate Zero-Crossings

for k = 1:numel(zxidx)
    x0(k) = fzero(@(x)Function(x,r),x(zxidx(k)));
end
x0(:)

ans = 4×1

-5.2360 -1.0472 1.0472 5.2360

figure
plot(x, y, '-b',  x0,zeros(size(x0)),'or')
grid

function [fx] = Function(x, r)
fx = r - 2*cos(x);
end

.

[Elena Boschet]

Thank you so much, real MVP! :)

[Star Strider]

As always, my pleasure!

Thank you!

.