Formulas are derived for computing a univalent mapping of the unit disc onto a radial slit domain with threefold circular symmetry. Goodman's upper bound for the univalent Bloch constant can be computed to a high degree of accuracy. A new upper bound is given for the universal constant which determines the lowest tone a membrane can produce if it contains no circular membrane with more than a specified radius. Copyright 2007 Rocky Mountain Mathematics Consortium.
