$ \text{Gegeben:}\\\text{Länge} \qquad b \qquad [m] \\ \text{Diagonale} \qquad d \qquad [m] \\ \\ \text{Gesucht:} \\\text{Breite} \qquad a \qquad [m] \\ \\ a = \sqrt{d^{2} -b^{2} }\\ \textbf{Gegeben:} \\ d=\frac{1}{2}m \qquad b=\frac{2}{5}m \qquad \\ \\ \textbf{Rechnung:} \\ a = \sqrt{d^{2} -b^{2} } \\ b=\frac{2}{5}m\\ d=\frac{1}{2}m\\ a = \sqrt{(\frac{1}{2}m)^{2} -(\frac{2}{5}m)^{2} }\\\\a=\frac{3}{10}m \\\\\\ \small \begin{array}{|l|} \hline d=\\ \hline \frac{1}{2} m \\ \hline 5 dm \\ \hline 50 cm \\ \hline 500 mm \\ \hline 5\cdot 10^{5} \mu m \\ \hline \end{array} \small \begin{array}{|l|} \hline b=\\ \hline \frac{2}{5} m \\ \hline 4 dm \\ \hline 40 cm \\ \hline 400 mm \\ \hline 4\cdot 10^{5} \mu m \\ \hline \end{array} \small \begin{array}{|l|} \hline a=\\ \hline \frac{3}{10} m \\ \hline 3 dm \\ \hline 30 cm \\ \hline 300 mm \\ \hline 3\cdot 10^{5} \mu m \\ \hline \end{array}$