от Добромир Глухаров » 25 Окт 2012, 15:02
4.) [tex]3-4i=\sqrt{3^2+4^2}e^{i.\(arctg\(-\frac{4}{3}\)+2k\pi\)}[/tex]
[tex](3-4i)^{2i}=5^{2i}e^{-2i^2\(arctg\frac{4}{3}-2k\pi\)}=e^{2iln5+2\(arctg\frac{4}{3}-2k\pi\)}=[/tex]
[tex]=e^{2arctg\frac{4}{3}-4k\pi}\(cos(2ln5)+i.sin(2ln5)\);\ k\in\mathbb{Z}[/tex]