0 个投票

I am trying to integrate this function using the code -
----------------
syms x
xd = 700/319
fun = ((x^4)* exp(x))/((exp(x) -1)^2);
cv = int(fun,0,xd)
--------------
But, I am getting same form of the function like that -
>> Cv_calculatior
cv =
int((x^4*exp(x))/(exp(x) - 1)^2, x, 0, 700/319)
What's wrong here??

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Torsten
Torsten 2022-5-27
编辑：Torsten 2022-5-27

0 个投票

Using "int", MATLAB tries to find an analytical antiderivative for your function, but cannot find one.
Use numerical integraion using "integral" instead. Don't start at 0 since your function has a division by zero at this location.
fun = @(x) x.^4.*exp(x)./(exp(x) -1).^2;
xd = 700/319;
result = integral(fun,1e-16,xd)

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Mohammad Humaun Kabir
编辑：Mohammad Humaun Kabir 2022-5-27
Thanks. Would you like to help me to write the whole code. Here is my problem -
Varying temparature from 0 degree to 800 degree with 2 degree interval ( T = 0:2:800)
integrating this function, y = ((x.^4).* exp(x))./((exp(x) -1).^2) for 0 to T, where T has a range of data
Expecting result: a list of data, T vs y
Torsten
Torsten 2022-5-27
fun = @(x) x.^4.*exp(x)./(exp(x) -1).^2;
T = [1e-16,2:2:800];
y(1) = 0;
for i = 2:numel(T)
y(i) = y(i-1) + integral(fun,T(i-1),T(i));
end
plot(T,y)

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