由欧拉公式：-i=cos(3π/2+2kπ)+isin(3π/2+2kπ)=e^((3π/2+2kπ)i)
所以z=ln(-i)=ln(e^((3π/2+2kπ)i))=(3π/2+2kπ)i
所以z的虚部(3π/2+2kπ)i,|z|=3π/2+2kπ, 幅角π/2 由欧拉公式：-i=cos(3π/2+2kπ)+isin(3π/2+2kπ)=e^((3π/2+2kπ)i)
所以z=ln(-i)=ln(e^((3π/2+2kπ)i))=(3π/2+2kπ)i
所以z的虚部(3π/2+2kπ)i,|z|=3π/2+2kπ, 幅角π/2