Calculating fπ in the consistent ladder approximation

We recalculate the pion decay constant fπ and the vacuum expectation value in a new ladder approximation scheme to the Schwinger-Dyson and Bethe-Salpeter equations which is consistent both with the axial Ward-Takahashi identity and Z2=1 condition (or the vector Ward identity in the abelian case). We find that our previous numerical results remain qualitatively unchanged: In particular, the Pagels-Stokar formula is a good approximation to fπ which agrees with the ladder-exact value to within 5%-30%. (orig.)