The Principle of Stationary Action

Varying the action

\displaystyle{S[q](t_1, t_2) = \int_{t_1}^{t_2} L \circ \Gamma[q]}

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The Principle of Stationary Action

\displaystyle{\delta_\eta S[q] (t_1, t_2) = 0}

\delta_\eta S[q] (t_1, t_2) = \int_{t_1}^{t_2} \delta_\eta L \circ \Gamma[q]

— Structure and Interpretation of Classical Mechanics

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2019.05.13 Monday ACHK