  We calculate the disk level S-matrix element of one Ramond-Ramond, two gauge
fields and one tachyon vertex operators in the world volume of non-BPS branes.
We then find the momentum expansion of this amplitude and show that the
infinite tachyon/massless poles and the contact terms of this amplitude can be
reproduced by the tachyon DBI and the WZ actions, and by their higher
derivative corrections.
