I have a Hamiltonian, consisting only of angular momentum components Lx,Ly,Lz. I need to go from it to some coordinate representation. But I don't have derivatives Lx' etc. in H. So, when I'll go to coordinates and momenta I'll have Hamiltonian equations like p_i=0, which doesn't have sense. How I need to go from H to x,y,z or \phi,\theta,r. H=-K1Lx2+K2Lz2+HxLx+HyLy+HzLz Going from L to angles can make no problem according to https://www.physicsforums.com/showthread.php?t=161865 in example But back?