Most physics students learn Lagrangian mechanics in their sophomore year. You can learn the fundamental ideas of Lagrangian mechanics only knowing a little Newtonian mechanics and multivariable calculus as taught in freshman year. I have included the above articles here so that you can understand “A short introduction to general relativity,” listed in the section “For physics majors,” and “the Hamiltonian formulation of classical mechanics’’ without obstacles. Also, it would be helpful to read our earlier article “Fermat’s principle and the consistency of physics,” before reading this article. For an alternative approach please see Chapter 2 of “The Feynman lectures on physics, volume 2” available at http://www.feynmanlectures.caltech.edu/II_19.html. The second article shows that conservation of angular momentum and centripetal force can be easily derived using Lagrangian mechanics.