  Recent experimental data for the differential decay distribution of the decay
$\tau^-\to\nu_\tau K_S\pi^-$ by the Belle collaboration are described by a
theoretical model which is composed of the contributing vector and scalar form
factors $F_+^{K\pi}(s)$ and $F_0^{K\pi}(s)$. Both form factors are constructed
such that they fulfil constraints posed by analyticity and unitarity. A good
description of the experimental measurement is achieved by incorporating two
vector resonances and working with a three-times subtracted dispersion relation
in order to suppress higher-energy contributions. The resonance parameters of
the charged $K^*(892)$ meson, defined as the pole of $F_+^{K\pi}(s)$ in the
complex $s$-plane, can be extracted, with the result $M_{K^*}=892.0 \pm 0.9
$MeV and $\Gamma_{K^*}=46.2 \pm 0.4 $MeV. Finally, employing the
three-subtracted dispersion relation allows to determine the slope and
curvature parameters $\lambda_+^{'}=(24.7\pm 0.8)\cdot 10^{-3}$ and
$\lambda_+^{''}=(12.0\pm 0.2)\cdot 10^{-4}$ of the vector form factor
$F_+^{K\pi}(s)$ directly from the data.
