How can I solve this problem in the matlab program ?

Question

Vuqar Samedov 2020-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/699235-how-can-i-solve-this-problem-in-the-matlab-program

回答： Walter Roberson 2020-12-22

采纳的回答： David Hill

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Vuqar Samedov 2020-12-21

Dear Walter Roberson, I use it in the matlab program, but the answer is not correct. I do not know why the answer is incorrect? The answer should actually be 1.

>> syms x a b

>> f=1/b*sqrt(2*pi)*exp(-1/2*b^2)*(x-a)^2;

>> u=(1/b*sqrt(2));

>> f=subs(f,u);

>> int (f,-inf,inf)

ans =

NaN

Timo Dietz 2020-12-21

Some parenthesis are missing and u seems to be wrongly defined. Nevertheless, Matlab seems to calculate intemediate steps which prevents the final elimination of values on symbolic side.

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Answer 1

David Hill 2020-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/699235-how-can-i-solve-this-problem-in-the-matlab-program#answer_581075

在 MATLAB Online 中打开

It does equal 1

syms u
int(exp(-u^2),-inf,inf);

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Timo Dietz 2020-12-21

Yes it does, but he substitution does not work as expected. Even with all parenthesis set and u defined correctly, Matlab seems to calculate intermediate values (e.g. sqrt(2)) and finally is not able to eliminate these.

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