(360k,360K+90)(360k+90,360K+180)(360k+180,360K+270)(360k+270,360K+360) (2kπ,2kπ+π/2)(2kπ+π/2,2kπ+π)(2kπ+π,2kπ+3π/2)(2kπ+3π/2,2kπ+2π)
