Re: Deriviation d/dt(x(t))

*To*: mathgroup at smc.vnet.net*Subject*: [mg27465] Re: Deriviation d/dt(x(t))*From*: "Kevin J. McCann" <KevinMcCann at home.com>*Date*: Tue, 27 Feb 2001 00:37:18 -0500 (EST)*References*: <97a6up$akb@smc.vnet.net> <R7mm6.17731$0r1.43554@ralph.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

circle = x^2 + y^2 ==r^2 SetAttributes[r,Constant] Dt[circle] > 2 x Dt[x,t] + 2 y Dt[y,t]==0 Kevin The wise words of DennisW555 on Mon, 26 Feb 2001 05:49:37 GMT: > >I have a problem, having a definition of a circle: x^2+y^2=r^2 > >Where x and y are functions of the time: x(t), y(t) and r ist a > >constant. > > > >Now I want to deriviate the equation to get the velocity vector. > >It should be : 2 x dx/dt +2 y dy/dt = 0 > > The velocity vector is simply {dx/dt, dydt} > >