2kπ<（2x+π/4）<2kπ+π/2；2kπ+3π/2<（2x+π/4）<2kπ+2π剩下就是解放程
X属于【2Kpai+pai/8,2Kpai+5pai/8】,K属于Z
pai/2+2kpai<=2x+pai/4<=3pai/2+2kpaipai/4+2kpai<=2x<=5pai/4+2kpaipai/8+kpai<=x<=5pai/8+kpai
