We give an interpretation of the hemisphere rigidity theorem Hang-Wang in framework Gelfand problem. More precisely, showed that for a metric $ g conformal to standard g_0 on S^{n}_{+} with R\geq n(n-1) and whose boundary coincides g_0|_{\partial S^{n}_{+}} $, then = $. This is related classical problem, which investigates -\Delta u \lambda g(u) certain nonlinearity bounded region \Omega \subse...