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

> 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?
>
> Christian Maier
>
>
>
>
>

```

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