Exponential function produces error with integrate command

Hello. I'm relatively new to Matlab, and I have the following problem which boils down from a larger, more complicated integral, but for now I am working with a simplified case. I believe that I have found the source of my problem.

I wrote

fun = @(x) (exp(x).*exp(-(x.^2)/2);
q = integral(fun,-1,Inf)

The value of q is then NaN.

Why is this the case? I evaluated this integral in Wolfram Alpha and received a number.

Answer 1

[David Goodmanson]

Hi Ben

for large x, exp(x) overflows to infinity before the exp(-(x.^2)/2) factor has a chance to bring in down. Try completing the square in the exponent:

fun = @(x) exp(-((x-1).^2)/2)*exp(1/2)

[Ben Miller]

That is what I suspected, and if I combine everything into one exp expression it works.