Question: asymptotic expansion

Dear all

for a fixed x positive, I would like to find an asymptotic expansion of the following integral when n goes to infinity. 

int(exp(-n*(x*cosh(t)+t)), t = 0 .. infinity)

Maybe we can define 
f:=n->int(exp(-n*(x*cosh(t)+t)), t = 0 .. infinity);
Then 

asympt(f(n), n,2)
But doesn't work

Many thanks for your help 

 

Please Wait...