  Cosmic expansion influences the angular size of black hole shadow. The most
general way to describe a black hole embedded into an expanding universe is to
use the McVittie metric. So far, the exact analytical solution for the shadow
size in the McVittie metric, valid for arbitrary law of expansion and arbitrary
position of the observer, has not been found. In this paper, we present the
first analytical solution for angular size of black hole shadow in McVittie
metric as seen by observer comoving with the cosmic expansion. We use a method
of matched asymptotic expansions to find approximate solution valid within the
entire range of possible positions of observer. As two particular examples, we
consider black hole in de Sitter and matter dominated universe.
