Symbolic Integration problem with respect to a variable

Question

Waleed El-Badry 2015-8-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/232193-symbolic-integration-problem-with-respect-to-a-variable

评论： Walter Roberson 2015-8-3

Hi, I wrote a simple script to calculate symbolic integration of multivariable with respect to "t" as below:

clear all
% Symbols in equation
syms c L Bita Gamma Eita t w a
% Function to be integrated
f=((Gamma*t/Eita)^(Bita-1))*(exp((Gamma*t/Eita)^Bita)*(a^(-t))-(t/w)*...
    ((Gamma*t/Eita)^(Bita-1))*(exp((Gamma*t/Eita)^Bita)*(a^(-t))));
f2=((Gamma*t/Eita)^(Bita-1))*(exp((Gamma*t/Eita)^Bita)*(a^(-t))*(1-(t/w)));
% Calculate the integral
R=(c*L*Bita)*(Gamma/Eita)*int(f,t,[0,w]);
R2=(c*L*Bita)*(Gamma/Eita)*int(f2,t,[0,w]);

The problem is result R and R2 are the same as the expression !

Your help is much appreciated.

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Answer 1

Sean de Wolski 2015-8-3

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https://ww2.mathworks.cn/matlabcentral/answers/232193-symbolic-integration-problem-with-respect-to-a-variable#answer_188093

http://www.mathworks.com/help/releases/R2015a/symbolic/int.html

Scroll down to the "Tips" section. Either int cannot find a solution or none exist.

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Walter Roberson 2015-8-3

Even if you substitute in exact numeric values for all of the symbolic variables except t, you are unlikely to arrive at a formula that has a closed form solution. There might be some special cases with some of the constants being 0 perhaps.

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