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

*To*: mathgroup at smc.vnet.net*Subject*: [mg27450] RE: [mg27407] Deriviation d/dt(x(t))*From*: "David Park" <djmp at earthlink.net>*Date*: Sun, 25 Feb 2001 20:55:56 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Christian, x[t]^2 + y[t]^2 == r^2 D[%, t] x[t]^2 + y[t]^2 == r^2 2*x[t]*Derivative[1][x][t] + 2*y[t]*Derivative[1][y][t] == 0 which displays as 2 x[t] x'[t] + 2 y[t] y'[t] == 0 David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ > From: Christian Maier [mailto:maier1 at sbox.tu-graz.ac.at] To: mathgroup at smc.vnet.net > > 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 > > Can anyone tell me how to do? > Thans in advance! > > Christian Maier > > > > >