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I need help understanding how to apply the formula for converting a Lagrangian to an equation of motion in this following specific application.

On page 4 of Zee's QTF in a Nutshell, he gives a Lagrangian (equation 1). In the following sentence he gives the corresponding equation of motion. I know the formula for converting a Lagrangian, but I don't get/understand Zee's answer. I have searched books and online without finding a similar worked out example.

Help is most appreciated. (I hope the formulas show below show up correctly.)

Thanks, Richard

(1) L = 1/2(∑_{a}m(dq_{a}/dt)^{2}- ∑_{a,b}k_{ab}q_{a}q_{b}- ......)

equation of motion => m(d^{2}q_{a}/dt^{2})a = - ∑_{b}K_{ab}q_{b}

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# Equation of Motion from Lagrangian - Zee QTF in a Nutshell

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