Integral representation of the modified Bessel function of the second kind
= Integral representation of the modified Bessel function of the second kind
For real $x>0$ and $\nu$, one useful representation is
$$
K_\nu(x)=\frac12\int_{-\infty}^{\infty}e^{-x\cosh t+\nu t}\,dt.
$$
It turns large-order asymptotics into a <Laplace integral> with a moving maximum.