Winkel/Einheitskreispunkt/Aufgabe

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${\displaystyle {}\angle ({\begin{pmatrix}1\\0\end{pmatrix}},{\begin{pmatrix}\cos \alpha \\\sin \alpha \end{pmatrix}})={\begin{cases}\alpha \,,{\text{ falls }}\alpha \leq \pi \,,\\2\pi -\alpha \,,{\text{ falls }}\alpha >\pi \,.\end{cases}}\,}$