Integration is not as I expect

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Abdulaziz Abutunis
Abdulaziz Abutunis am 31 Mär. 2015
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

Akzeptierte Antwort

John D'Errico
John D'Errico am 31 Mär. 2015
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.
  2 Kommentare
Abdulaziz Abutunis
Abdulaziz Abutunis am 31 Mär. 2015
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 am 1 Apr. 2015
You are right thanks

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