Even non-constant meromorphic function in the complex plane has branches of
the inverse that are definied in spherical discs of radii arbitrarily clos
e to arctan root 8 approximate to 70 degrees 32'. This constant is best pos
sible. The proof depends oil the study of singular surfaces associated with
meromorphic functions. (C) 1999 Academie des sciences/Editions scientifiqu
es et medicales Elsevier SAS.