a simple question about EulerEquations

*To*: mathgroup at smc.vnet.net*Subject*: [mg96059] a simple question about EulerEquations*From*: kem <kemelmi at gmail.com>*Date*: Wed, 4 Feb 2009 05:17:29 -0500 (EST)

Hi, It seems that mathematica gives a different expression for Euler- Lagrange equation. Isn't the answer to: EulerEquations[ f[u'[x],u[x],x] , u[x] , x] should be: Derivative[0, 1, 0][f][Derivative[1][u][x], u[x], x] - Derivative[1, 0, 1][f][Derivative[1][u][x], u[x], x] ==0 ? The output that I am getting from mathematica is: Derivative[0, 1, 0][f][Derivative[1][u][x], u[x], x] - Derivative[1, 0, 1][f][Derivative[1][u][x], u[x], x] - Derivative[1][u][x]* Derivative[1, 1, 0][f][Derivative[1][u][x], u[x], x] - Derivative[2][u][x]* Derivative[2, 0, 0][f][Derivative[1][u][x], u[x], x] == 0 Thank you