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non-linear equations not covered by built-in procedures

• To: mathgroup at smc.vnet.net
• Subject: [mg38809] non-linear equations not covered by built-in procedures
• From: mathma18 at hotmail.com ("Narasimham G.L.")
• Date: Tue, 14 Jan 2003 06:10:37 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

Hi,

I am a beginner with Mathematica. Apprecite help for non-linear
diffrl. equns.

eqn = r''[t] + 1/r[t] == 0
sol = DSolve[{eqn, r[0] == 1, r'[0] == 0}, r[t], t]
Plot[r[t] /. sol, {t, 0, 2Pi }]

   carries error msg >>  DSolve::dnim: 
   Built-in procedures cannot solve this differential equation.

The linear case when 1/r[t] is replaced by r[t] works OK,yields the
expected Cos[t] solution.
Is there a web accessible Mathematica reference for ODEs, non linear,
PDEs etc.? 

Regards

• Follow-Ups:
  • Re: non-linear equations not covered by built-in procedures
    • From: "Bobby R. Treat" <majort@cox-internet.com>