Explicit integral not found

Question

I get the well-known error "Explicit integral cannot be found" if I try to evaluate the following integral

syms z;
funz=1./(1+exp((z*z-0.5)/0.1));
Integ2=int(funz,z,0,inf)

I get a warning:

Warning: Explicit integral could not be found.        
Integ2 =   
int(1/(exp(10*z^2 - 5) + 1), z == 0..Inf)

Mathematics estimates this integral on 0.693.

I tried replacing the lower limit of integration with some small finite number (0.001), but that does not help. Please help in determining the fix for this problem. Any help is appreciated. Many thanks!

Answer 1

Try arithmetic variable accuracy , 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

. , " ". :

int , vpa.