2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/129259We get a local existence result in $H^s$ with $s>3/2$ for second order quasilinear wave equation with radial initial data in 2+1 dimensions, based on an improvement of Strichartz estimate in the radial case. Moreover, we get the corresponding local well-posed result for semilinear wave equation. The required index of regularity here is 1/4 less than the index 7/4, which is essentially sharp in general.19pages, no figuresAnalysis of PDEs35L15; 35L70text