How can I fix this? am trying to find the value of p with bisection method

Question

Nikolas 2022-10-30

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1839363-how-can-i-fix-this-am-trying-to-find-the-value-of-p-with-bisection-method

回答： Shubham Dhanda 2023-6-21

syms p
x = 13.61015;
y = 13257;
a = 5.14;
b = 11.47;
c = 0;
f = (x^3 + p^2*x^2 - 10)*sin(x) == 0;
%eqn = y - (x^3 + p^2*x^2 - 10)*sin(x) == 0;
%p = vpasolve(eqn,p);
%p = p(p>a & p<b);
i=0;
while (x^3 + a^2*x^2 - 10)*sin(x) * (x^3 + b^2*x^2 - 10)*sin(x) > 0 && i<5 ;
    b = (a+b)/2;
    i=i+1;
end
disp (b);

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Jan 2022-10-30

If you ask for a fixing, it is useful to mention, which problem you have. It is easier to solve a problem than to guess, what the problem is.

The bisection method is a numerical approximation. Why do you choose a symbolic variable? You define f, but do not use it anywhere.

Search in the net for "bisection method". Look in Matlab's FileExchange. Your code has only some few similarities with it.

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Answer 1

Shubham Dhanda 2023-6-21

0
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在 MATLAB Online 中打开

Hi,

I understand that you want to find the root of the equation f using bisection method.

To fix the code, define the value of p initially and then inside the while loop, calculate the value of p using the bisection method.

Below is the MATLAB code implementation of the problem:

syms p
x = 13.61015;
y = 13257;
a = 5.14;
b = 11.47;
c = 0;
i = 0;
p = (a + b)/2;
while abs(x^3 + p^2*x^2 - 10)*sin(x) > c && i < 5
    if (x^3 + a^2*x^2 - 10)*sin(x) * (x^3 + p^2*x^2 - 10)*sin(x) > 0 
        a = p;
    else
        b = p;
    end
    p = (a + b)/2;
    i = i + 1;
end
disp(p);
   11.3711