1. The problem statement, all variables and given/known data Let J-hat be a quantum mechanial angular momentum operator. The commutator [J^hat_x J^hat_y,J^hat_z] is equivalent to which of the following 2. Relevant equations [J^hat_x,J^hat_y]=iħJ^hat_z [J^hat_y,J^hat_z]=iħJ^hat_x [J^hat_z,J^hat_x]=iħJ^hat_y [A,B]=[AB-BA] 3. The attempt at a solution I tried to plug this out using commutator relations [J^hat_x J^hat_y,J^hat_z]=J^hat_x J*hat_y J^hat_x-J^hat_xJ^hat_x J^hat_y simplifies to iħ(j^hat_z-J^hat_x)=0 The answer the got for the practice test is -i=(j^hat_x,J^hat_z) im not sure how the simplified to get this answer. if i simplified mine i would just get J^hat_z=J^hat_x..