مکانیک لاگرانژی

${\displaystyle L=T-V\!}$

${\displaystyle S=\int _{0}^{T}{({{1} \over {2}}m{\dot {x}}^{2}-V(x))dt}}$

${\displaystyle {\partial L \over {\partial x}}-{d \over {dt}}{\partial L \over {\partial {\dot {x}}}}=0}$

${\displaystyle m{\ddot {x}}=-{\partial V \over \partial x}=F}$