Searching for help: Warning: Explicit integral could not be found.

Question

Andreas 2013-9-9

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https://ww2.mathworks.cn/matlabcentral/answers/86718-searching-for-help-warning-explicit-integral-could-not-be-found

Hello,

I'm trying to find an integral for a function, but there is always an Error Message: Warning: Explicit integral could not be found.

The function include two variables:

syms H positive;
syms x;

and looks like this:

f = (40000*(5962725554385875/(9223372036854775808*(40000*((5000*x - 75)^2 + 81/(256*H^2))^(1/2) + 1)) + 5690802099995323/18446744073709551616)*((5000*x - 75)^2 + 81/(256*H^2))^(1/2) - (3162897844476069375*1000^((235758936893218125*((5000*x - 75)^2 + 81/(256*H^2))^(1/2))/1125899906842624 + 10588771210153143/576460752303423488)*((5000*x - 75)^2 + 81/(256*H^2))^(1/2))/549755813888)

I tried:

F = int(f,x,0,B) % with B=0.03 (previously set)

but there is always the Error Message. If anybody have a clue please answer. Btw, the same problem occurs at another function:

g = -(40000*((5000*x - 75)^2 + 81/(256*H^2))^(1/2))/((3330505768082351*(40000*((5000*x - 75)^2 + 81/(256*H^2))^(1/2))^(95251/50000))/9007199254740992 - 811793349164925/274877906944)
G = int(g,x,0,B)

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Answer 1

Walter Roberson 2013-9-9

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You cannot realistically integrate that f, unless perhaps H is fairly large. If you evaluate f at x=0, H=17, then you will get a value on the order of -6E47122 . The largest f(x) is at x=3/200; with H=17, it is still -1.2E26. The function is symmetric, so by x=3/100 it is back down to -6E47122

I have poked around but I see no reason to expect that there might be a closed form for the symbolic integral.