how to get a value using integral

2018 5 11
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更新时间：2018 5 11
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hello, I have a trouble to get value using integral.
My question is
so, I use
syms x
double(int(x^3.5/(x-1)^(1/2),0,1)) % vpa(int(x^3.5/(x-1)^(1/2),0,1))
but I got error or numeric::int even though the real solution is -0.859029i. So Do you have any ideas to solve this problem???

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David Goodmanson
David Goodmanson 2018-5-11
编辑：David Goodmanson 2018-5-11

0 个投票

Hello Jongnam, try
format long
fun = @(x) x.^(7/2)./(sqrt(x-1))
integral(fun,0,1)
ans = 0.000000000000000 - 0.859029241215738i
As a check, with the substitution x = sin(theta)^2 you can arrive at (-i) *
2*Integral{0,pi/2} sin(theta)^8 dtheta
= (7*5*3*1)/(8*6*4*2)*pi
ans = 0.859029241215959

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