  The light curve of an exoplanetary transit can be used to estimate the
planetary radius and other parameters of interest. Because accurate parameter
estimation is a non-analytic and computationally intensive problem, it is often
useful to have analytic approximations for the parameters as well as their
uncertainties and covariances. Here we give such formulas, for the case of an
exoplanet transiting a star with a uniform brightness distribution. We also
assess the advantages of some relatively uncorrelated parameter sets for
fitting actual data. When limb darkening is significant, our parameter sets are
still useful, although our analytic formulas underpredict the covariances and
uncertainties.
