Hey all, I have a question with first Brillouin zone. It's: It says that it's enough to consider values of K within the first brillouin zone, K= [-pi/a,pi/a). why is this easy to see, and why don't we choose the interval K= (0 , 2pi/a) instead? Why is the point K=pi/a not included (open interval)? I know that according to periodicity we get that if we solve for the first Billiouin zone then we know the solution in the whole lattice. But why just in this interval?