  We study harmonically trapped two-species Bose-Einstein condensates within
the Gross-Pitaevskii formalism. By invoking the Thomas-Fermi approximation, we
derive an analytical solution for the miscible ground state in a particular
region of the system's parameter space. This solution furnishes a simple
formula for determining the relative strength of the interspecies interaction
from a measurement of the density distribution of only one of the two species.
Accompanying numerical simulations confirm its accuracy for sufficiently large
numbers of condensed particles. The introduced formula provides a
condensate-based scheme that complements the typical experimental methods of
evaluating interspecies scattering lengths from collisional measurements on
thermal samples.
