How to get the Lagrangian that generates certain diff equation ?

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To derive a Lagrangian that corresponds to a specific second-order ordinary differential equation, one can refer to the 'inverse problem of variational calculus.' Key resources include N. Akhiezer's "The Calculus of Variations," which provides a one-dimensional example, and R. Santilli's "Foundations of Theoretical Mechanics," which offers methods for both one-dimensional and multi-dimensional cases. Santilli's works detail approaches such as Kobussen's method and the inverse Legendre transformation for obtaining the Lagrangian from the Hamiltonian. Practical references are preferred over general theorems or complex geometrical explanations. These texts serve as essential guides for those seeking to understand the relationship between differential equations and Lagrangian mechanics.
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how to get the Lagrangian that generates certain diff equation ?

I have an ordinary differential equation of second order. I am looking for the Lagrangian(s) for which this equation is the Euler-Lagrange equation. I need a practical reference specifically written for one degree of freedom (one equation), I'm not interested in general theorems of existence or highly geometrical language. I found some reference by Darboux in 1894 but its in French. Any english reference?
 
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Got it. The problem is known as 'inverse problem of variational calculus'. For future references:

N. Akhiezer, "The Calculus of Variations", 1962:

page 166: example of 1D problem

R. Santilli, "Foundations of Theoretical Mechanics II", Springer-Verlag, 1983:

page 353: reworking the same example as Akhiezer
page 315: by knowing one first integral, Kobussen's method

R. Santilli, "Foundations of Theoretical Mechanics I", Springer-Verlag, 1978:

page 201: Douglas approach for n-dimension, easily applied to n=1
page 208: first obtaining Hamiltonian and then get the Lagrangian through inverse Legendre transformation
 
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smallphi said:
Got it. The problem is known as 'inverse problem of variational calculus'. For future references:

N. Akhiezer, "The Calculus of Variations", 1962:

page 166: example of 1D problem

R. Santilli, "Foundations of Theoretical Mechanics II", Springer-Verlag, 1983:

page 353: reworking the same example as Akhiezer
page 315: by knowing one first integral, Kobussen's method

R. Santilli, "Foundations of Theoretical Mechanics I", Springer-Verlag, 1978:

page 201: Douglas approach for n-dimension, easily applied to n=1
page 208: first obtaining Hamiltonian and then get the Lagrangian through inverse Legendre transformation

Thanks for the pointers!
 
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