Bisection method relative error

Question

Sazcl 2022-3-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1673789-bisection-method-relative-error

评论： Jan 2023-8-2

采纳的回答： Mohammed Hamaidi

在 MATLAB Online 中打开

Hello everyone, I don't use MATLAB very well. I have a question. If you can help, I'd appreciate.

I have a function below that I have to find its roots using bisection method. I want the for loop to stop on the point where relative error is lower than %0.05. I couldn't understand how I can define n.

f=@(x) log(x)-cos(x)-exp(-x);
x1=1;
x2=2;
xmid=(x1+x2)/2
for i=1:n;
    if (f(xmid)*f(x2))<0
        x1=xmid;
    else
        x2=xmid;
    end
    xmid=(x1+x2)/2;
    
end
fprintf('The root is: %3.8g\n',xmid)

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Answer 1

Mohammed Hamaidi 2022-3-17

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1673789-bisection-method-relative-error#answer_919969

编辑：Mohammed Hamaidi 2022-3-18

在 MATLAB Online 中打开

Hi

Just use "while" loop with your condition as follows:

f=@(x) log(x)-cos(x)-exp(-x);
x1=1;
x2=2;
xmid=(x1+x2)/2;
while (x2-x1)>0.0005
    if (f(xmid)*f(x2))<0
        x1=xmid;
    else
        x2=xmid;
    end
    xmid=(x1+x2)/2;    
end
fprintf('The root is: %3.8g\n',xmid)