Re: Is this so hard?

*To*: mathgroup at smc.vnet.net*Subject*: [mg95270] Re: Is this so hard?*From*: "Steve Luttrell" <steve at _removemefirst_luttrell.org.uk>*Date*: Wed, 14 Jan 2009 05:50:53 -0500 (EST)*References*: <200901111138.GAA12346@smc.vnet.net> <gkgq3p$4a2$1@smc.vnet.net> <gkh0vt$6ia$1@smc.vnet.net>

Try solving it numerically. t0 = 1.12; sol = NDSolve[{x''[t] == 1/x[t]^2, x[0] == -1, x'[0] == 0}, x, {t, 0, t0}] Plot[(x /. sol[[1]])[t], {t, 0, t0}] This gives the following error message: "NDSolve::ndsz: At t == 1.1107203590726262`, step size is effectively zero; singularity or stiff system suspected." There is a singularity where x[t] goes to zero, which makes the 1/x[t]^2 term in the ODE blow up. -- Stephen Luttrell West Malvern, UK "cool-RR" <ram.rachum at gmail.com> wrote in message news:gkh0vt$6ia$1 at smc.vnet.net... > >> You didn't want another initial (or boundary) condition for this 2nd >> order ODE? >> > > You're right. > > DSolve[{x''[t] == 1/x[t]^2, x[0] == -1, x'[0] == 0}, x, t] > > This still gives no answer. > > Any ideas? >