Using the incremental search method or otherwise to locate one root of the function

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John wick 2019-9-13

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https://ww2.mathworks.cn/matlabcentral/answers/480263-using-the-incremental-search-method-or-otherwise-to-locate-one-root-of-the-function

评论： Adam 2019-9-13

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Use Matlab's fzero function or your own method to locate all roots of the function,

f ( x ) = cos ( − 5 x ^3 + 6 x ^2 + 4 x − 3 )

on the interval [1,2] if they exist then plot the function on the interval marking the roots with red circles of size 3.

If there are no roots on your interval then use the incremental search method or otherwise to locate one root of the function and plot it with a red circle of size 3 along with the function.

I have arrived with the code down below but is there a way to add the one that says "If no roots" in the code below

f = @(x)cos(-5.*x.^3+6.*x.^2+4x-3);
fplot(f,[1,2]);
hold on;
for n = 1:0.1:2
k = fzero(f,n);
plot(k, 0,'ro','MarkerSize',3);
end

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John wick 2019-9-13

编辑：John wick 2019-9-13

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Thank you for the comment!

So as i should change, it should be something like this in order for it to answer the problem of if no roots. Other structure is fine so i only need to change the fzero part.

f = @(x)cos(-5.*x.^3+6.*x.^2+4.*x-3);
fplot(f,[1,2]);
hold on;
for n = 1:0.1:2
[k,fval,exitflag,output] = fzero(f,n);
plot(k, 0,'ro','MarkerSize',3);
end