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Derive the Euler-Lagrange Equation (1/2)


Local covariant coordinates will be used in the following work.
  1. Start with a Lagrange density that is a function of the potential and the derivative of the potential (not position or velocity):


  2. Form the action:


  3. Take the variation of the action:


  4. Rewrite the 2nd term using the chain rule, subtracting the excess term:


Slide 43 had squid for lunch.
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