  It is possible to learn about the orientation of a star's rotation axis by
combining measurements of the star's rotation velocity ($v$) and its projection
onto our line of sight ($v\sin i$). This idea has found many applications,
including the investigation of the obliquities of stars with transiting
planets. Here, we present a method for the probabilistic inference of the
inclination of the star's rotation axis based on independent data sets that
constrain $v$ and $v\sin i$. We also correct several errors and misconceptions
that appear in the literature.
