$
\text{Gegeben:}\\\text{Winkel} \qquad \alpha \qquad [^{\circ}] \\
\\ \text{Gesucht:} \\\text{Kosinus alpha} \qquad cos \alpha \qquad [] \\
\\ cos \alpha = \sqrt{1 - sin^{2} \alpha }\\ \textbf{Gegeben:} \\ \alpha=90^{\circ} \qquad \\ \\ \textbf{Rechnung:} \\
cos \alpha = \sqrt{1 - sin^{2} \alpha } \\
\alpha=90^{\circ}\\
cos 90^{\circ} = \sqrt{1 - sin^{2} 90^{\circ} }\\\\cos 90^{\circ}=0
\\\\\\ \small \begin{array}{|l|} \hline alpha=\\ \hline 90 ° \\ \hline 5,4\cdot 10^{3} \text{'} \\ \hline 3,24\cdot 10^{5} \text{''} \\ \hline 100 gon \\ \hline 1,57 rad \\ \hline \end{array} \small \begin{array}{|l|} \hline cosalpha=\\ \hline 0 rad \\ \hline 0 mrad \\ \hline 0 ^\circ \\ \hline 0 \text{'} \\ \hline 0 \text{'''} \\ \hline \end{array}$