设点P的坐标为(x,y),则：
x=2×cos2π/3
=2×cos(π-π/3)
=2×(-cosπ/3)
=2×(-1/2)
=-1
y=2×sin2π/3
=2×sin(π-π/3)
=2×sinπ/3
=2×(√3)/2
=√3
点P的坐标为(-1,√3)