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Integration is not as I expect

조회 수: 1 (최근 30일)
Abdulaziz Abutunis
Abdulaziz Abutunis 2015년 3월 31일
댓글: Abdulaziz Abutunis 2015년 4월 1일
Hi all, Please I have an integration I am trying to solve using matlab. The integration derived me crazy because i know the output and matlab does not give me the same answer.
my code is simple and as follow
syms U_0 x L v X
U=U_0*(1-(x/L));
y=((((0.45*v)/(U^6))*(int(U^5,x,0,x))))
The answer I got is
y= (3*v*x*(6*L^5 - 15*L^4*x + 20*L^3*x^2 - 15*L^2*x^3 + 6*L*x^4 - x^5))/(40*L^5*U_0*(x/L - 1)^6)
While the right answer I should receive is
y= (0.075*L*v*(1/(x/L - 1)^6 - 1))/U_0

채택된 답변

John D'Errico
John D'Errico 2015년 3월 31일
And you are absolutely positive that the two forms are not mathematically equivalent? You have checked that carefully?
The thing about symbolic computations is the computer need not return a result that is in exactly the form you recognize. That need not make it wrong.
So why not look more carefully at that result? You might surprise yourself.
  댓글 수: 2
Abdulaziz Abutunis
Abdulaziz Abutunis 2015년 3월 31일
Thank you John for your response. I just supstract the equations from each other and the results was not zero. I do not know if there is a way in matlab that turn equations in particular format. I try simplify no thing was changed. I will try to simplify it by hand. Thanks again
Abdulaziz Abutunis
Abdulaziz Abutunis 2015년 4월 1일
You are right thanks

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