от Добромир Глухаров » 13 Яну 2010, 15:18
[tex]1.)\ x=\sqrt[3]{2i} ,\ 2i=2(cos{\frac{\pi }{2 }} +i.sin{\frac{\pi }{2 }} )[/tex]
[tex]x_k=\sqrt[3]{2}(cos{\frac{\frac{\pi }{2 }+2k\pi}{3}} +i.sin{\frac{\frac{\pi }{2 }+2k\pi}{3}} ),\ k=0,1,2.[/tex]
[tex]x_0=\sqrt[3]{2}(cos{\frac{\pi }{6 }}+i.sin{ \frac{\pi }{6 }})=\sqrt[3]{2}(\frac{\sqrt{3} }{2 } +i.\frac{1}{2 })[/tex]
[tex]x_1=\sqrt[3]{2}(cos{\frac{5\pi }{6 }}+i.sin{ \frac{5\pi }{6 }})=\sqrt[3]{2}(-\frac{\sqrt{3} }{2 } +i.\frac{1}{2 })[/tex]
[tex]x_2=\sqrt[3]{2}(cos{\frac{3\pi }{2 }}+i.sin{ \frac{3\pi }{2 }})=\sqrt[3]{2}[0 +i.(-1)]=-\sqrt[3]{2}.i[/tex]