Mocniny a odmocniny komplexních čísel

2010013409

Část: 
C
Tři kořeny rovnice \[ x^{4} + 8\mathrm{i} = 0 \] jsou \[\begin{aligned}x_{1} = \root{4}\of{8}\left (\cos \frac{3}{8}\pi + \mathrm{i}\sin \frac{3}{8}\pi \right ), \\ x_{2} = \root{4}\of{8}\left (\cos \frac{7}{8}\pi + \mathrm{i}\sin \frac{7}{8}\pi \right ),\\ x_{3} = \root{4}\of{8}\left (\cos \frac{15}{8}\pi + \mathrm{i}\sin \frac{15}{8}\pi \right ).\\ \end{aligned}\] Určete čtvrtý kořen.
\(x_{4} = \root{4}\of{8}\left (\cos \frac{11}{8}\pi + \mathrm{i}\sin \frac{11}{8}\pi \right )\)
\(x_{4} = \root{4}\of{8}\left (\cos \frac{9}{8}\pi + \mathrm{i}\sin \frac{9}{8}\pi \right )\)
\(x_{4} = \root{4}\of{8}\left (\cos \frac{5}{8}\pi + \mathrm{i}\sin \frac{5}{8}\pi \right )\)
\(x_{4} = \root{4}\of{8}\left (\cos \frac{1}{8}\pi + \mathrm{i}\sin \frac{1}{8}\pi \right )\)

2010013412

Část: 
C
Které z čísel nepatří do množiny řešení dané rovnice? \[x^{4}-1+\mathrm{i}=0\]
\(\root{8}\of{2}\left (\cos \frac{3\pi}{16} + \mathrm{i}\sin \frac{3\pi}{16}\right )\)
\(-\root{4}\of{1-\mathrm{i}}\)
\(-\mathrm{i}\root{4}\of{1-\mathrm{i}}\)
\(\root{8}\of{2}\left (\cos \left(-\frac{\pi}{16}\right) + \mathrm{i}\sin \left(-\frac{\pi}{16}\right)\right )\)

2010013413

Část: 
C
Které z čísel nepatří do množiny řešení dané rovnice? \[x^{4}+1+\mathrm{i}=0\]
\(\root{8}\of{2}\left (\cos \frac{3\pi}{16} + \mathrm{i}\sin \frac{3\pi}{16}\right )\)
\(\mathrm{i}\root{4}\of{-1-\mathrm{i}}\)
\(\root{4}\of{-1-\mathrm{i}}\)
\(\root{8}\of{2}\left (\cos \frac{5\pi}{16} + \mathrm{i}\sin \frac{5\pi}{16}\right )\)

9000034303

Část: 
C
Množinou všech komplexních řešení rovnice \(x^{3} + \mathrm{i} = 0\) je:
\(\{\mathrm{i};\ \frac{\sqrt{3}} {2} -\frac{1} {2}\mathrm{i};\ -\frac{\sqrt{3}} {2} -\frac{1} {2}\mathrm{i}\}\)
\(\{ - 1;\ -\frac{\sqrt{3}} {2} + \frac{1} {2}\mathrm{i};\ -\frac{\sqrt{3}} {2} -\frac{1} {2}\mathrm{i}\}\)
\(\{ - 1;\ \frac{\sqrt{3}} {2} -\frac{1} {2}\mathrm{i};\ -\frac{\sqrt{3}} {2} -\frac{1} {2}\mathrm{i}\}\)
\(\{\mathrm{i};\ -\frac{\sqrt{3}} {2} + \frac{1} {2}\mathrm{i};\ -\frac{\sqrt{3}} {2} -\frac{1} {2}\mathrm{i}\}\)

9000034308

Část: 
C
Dvě z řešení rovnice \[x^{3} + 1 + \mathrm{i} = 0\] jsou \[ x_{1} = \root{6}\of{2}\left (\cos \frac{5} {12}\pi + \mathrm{i}\sin \frac{5} {12}\pi \right ), \] \[ x_{2} = \root{6}\of{2}\left (\cos \frac{13} {12}\pi + \mathrm{i}\sin \frac{13} {12}\pi \right ). \] Třetím řešení rovnice je:
\(x_{3} = \root{6}\of{2}\left (\cos \frac{21} {12}\pi + \mathrm{i}\sin \frac{21} {12}\pi \right )\)
\(x_{3} = \root{6}\of{2}\left (\cos \frac{9} {12}\pi + \mathrm{i}\sin \frac{9} {12}\pi \right )\)
\(x_{3} = \root{6}\of{2}\left (\cos \frac{17} {12}\pi + \mathrm{i}\sin \frac{17} {12}\pi \right )\)
\(x_{3} = \root{6}\of{2}\left (\cos \frac{19} {12}\pi + \mathrm{i}\sin \frac{19} {12}\pi \right )\)

9000035810

Část: 
C
Je dáno komplexní číslo \(z = -2 + 2\mathrm{i}\). Všechny navzájem různé hodnoty \(\root{3}\of{z}\) jsou:
\(\begin{aligned}[t] &w_{0} = \root{6}\of{8}\left (\cos \frac{\pi } {4} + \mathrm{i}\sin \frac{\pi } {4}\right ) & \\&w_{1} = \root{6}\of{8}\left (\cos \frac{11\pi } {12} + \mathrm{i}\sin \frac{11\pi } {12}\right ) \\&w_{2} = \root{6}\of{8}\left (\cos \frac{19\pi } {12} + \mathrm{i}\sin \frac{19\pi } {12}\right ) \\ \end{aligned}\)
\(\begin{aligned}[t] &w_{0} = 2\left (\cos \frac{\pi } {4} + \mathrm{i}\sin \frac{\pi } {4}\right ) & \\&w_{1} = 2\left (\cos \frac{11\pi } {12} + \mathrm{i}\sin \frac{11\pi } {12}\right ) \\&w_{2} = 2\left (\cos \frac{19\pi } {12} + \mathrm{i}\sin \frac{19\pi } {12}\right ) \\ \end{aligned}\)
\(\root{3}\of{-2} + \root{3}\of{2}\)
\(\begin{aligned}[t] &w_{0} = 2\left (\cos \frac{\pi } {3} + \mathrm{i}\sin \frac{\pi } {3}\right )& \\&w_{1} = 2\left (\cos \pi +\mathrm{i}\sin \pi \right ) \\&w_{2} = 2\left (\cos \frac{5\pi } {3} + \mathrm{i}\sin \frac{5\pi } {3}\right ) \\ \end{aligned}\)