本文介绍了找不到明确的积分的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
如果我尝试评估以下积分，我将收到一个众所周知的错误:找不到明确的积分"
I am getting a well-known error of "Explicit integral could not be found" if I try to evaluate following integral
syms z;
funz=1./(1+exp((z*z-0.5)/0.1));
Integ2=int(funz,z,0,inf)
我得到警告:
Warning: Explicit integral could not be found.
Integ2 =
int(1/(exp(10*z^2 - 5) + 1), z == 0..Inf)
Mathematica将该积分评估为0.693.
Mathematica evaluates this integral to 0.693.
我尝试将积分下限替换为较小的有限数字(0.001)，但这无济于事.请帮助确定解决此问题的方法.任何帮助表示赞赏.非常感谢！
I have tried replacing lower integration limit to some small finite number (0.001) but that doesn't help.Please help in identifying the fix for this problem.Any help is appreciated.Thanks a lot !
推荐答案
尝试可变精度算术，vpa:
syms z;
funz=1./(1+exp((z*z-0.5)/0.1));
Integ2=int(funz,z,0,inf)
Warning: Explicit integral could not be found.
Integ2 =
int(1/(exp(10*z^2 - 5) + 1), z = 0..Inf)
vpa(Integ2,5) % 5 is the number of significant digits
ans =
0.69305
请参见文档近似定积分"中的最后一个示例.引用:
See the last example in the documentation, "Approximate Definite Integrals".Quote:
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