2kπ+3π/2<α<2kπ+2π2kπ/3+π/2<α/3<2kπ/3+2π/3k=0α/3在第二象限k=12π/3+π/2=7π/62π/3+2π/3=4π/3α/3在第三象限k=24π/3+π/2=11π/64π/3+2π/3=2π在第4象限。所以2,3,4象限。
