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MathGroup Archive 2001

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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg27437] Re: Deriviation d/dt(x(t))
  • From: Hendrik van Hees <h.vanhees at gsi.de>
  • Date: Sun, 25 Feb 2001 20:55:41 -0500 (EST)
  • References: <97a6up$akb@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Christian Maier wrote:
> 
> 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?

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In[1]:= rSqr=x^2+y^2;

In[2]:= Dt[rSqr,t]

Out[2]= 2 x Dt[x, t] + 2 y Dt[y, t]

Hope that helps ;-).

-- 
Hendrik van Hees		Phone:  ++49 6159 71-2751
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