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Re: question about ODE

  • To: mathgroup at smc.vnet.net
  • Subject: [mg117868] Re: question about ODE
  • From: Daniel Lichtblau <danl at wolfram.com>
  • Date: Sat, 2 Apr 2011 02:42:10 -0500 (EST)

??????? ??????? wrote:
> Hello Everybody! Please help me to find answer on this question
> 
> How can I solve this ODE
> 
> x''[t]=-NIntegrate[Sin[x'[t]*L], {L,0,1}] , x[0]=0, x'[0]=10
> 
> The integral in this ODE must be evalueted in each step of solving ODE. But I don't know how can I realise it.

The integral is not a function of x or t, and it can be handled 
symbolically, so you can simply integrate in advance.

In[3]:= NDSolve[{x''[t]==Evaluate[ Integrate[Sin[x'[t]*L], {L,0,1}]],
         x[0]==0, x'[0]==10}, x[t], {t,0,5}]

Out[3]= {{x[t] -> InterpolatingFunction[{{0., 5.}}, <>][t]}}

Daniel Lichtblau
Wolfram Research



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