Minimizing the Functional for the Brachistochrone Problem

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SUMMARY

The discussion focuses on minimizing the functional for the Brachistochrone problem using the Euler-Lagrange equation. The functional to minimize is defined as T[y]=∫(x_0 to x_1) (dx/√x)√(1+(dy/dx)²), with the proposed solution being y(x)=√(x(2r-x))+2r ArcSin(x/2r). Participants express confusion regarding the validity of the solution, questioning whether it represents a true Brachistochrone curve.

PREREQUISITES
  • Understanding of calculus, specifically integration and differentiation.
  • Familiarity with the Euler-Lagrange equation in the context of variational calculus.
  • Knowledge of the Brachistochrone problem and its historical significance in physics.
  • Ability to manipulate and interpret mathematical functions and equations.
NEXT STEPS
  • Study the derivation and application of the Euler-Lagrange equation in variational problems.
  • Explore the historical context and solutions of the Brachistochrone problem in classical mechanics.
  • Learn about the properties of Brachistochrone curves and their implications in physics.
  • Investigate numerical methods for solving variational problems and their applications.
USEFUL FOR

Students of physics and mathematics, particularly those studying calculus of variations and classical mechanics, as well as educators seeking to clarify the Brachistochrone problem and its solutions.

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Homework Statement



So if +x points downward and +y points rightwards then the functional that needs to be minimized is:

\sqrt{2g}T[y]=\int_{x_0}^{x_1}\frac{dx}{\sqrt{x}}\sqrt{1+\left(\frac{dy}{dx}\right)^2}


Homework Equations



I think we just have to use the Euler lagrange equation. The book (Hand and Finch says) the solution is:

y(x)=\sqrt{x(2r-x)}+2r ArcSin\left(\frac{x}{2r}\right)

This is not even a brachistrone curve! Am I missing something?
 
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The Attempt at a SolutionI have tried to use the Euler Lagrange equation but I just can't seem to get the answer that is given. Any help would be greatly appreciated!
 

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