==== Lösung ====
\begin{align*}
R &= \rho_{Cu,20°C} \cdot \frac{l}{A} && | \text{mit } A = r^2 \cdot \pi = \frac{1}{4} d^2 \cdot \pi \\
R &= \rho_{Cu,20°C} \cdot \frac{4 \cdot l}{d^2 \cdot \pi} && \\
\end{align*}
==== Endergebnis ====
\begin{align*}
R &= 5,666 \Omega \rightarrow 5,7 \Omega \\
\end{align*}
\begin{align*}
R &= @@R =rho * (4 * l) / (d^2 * pi)@@ @@ Unit = "Omega" @@ \rightarrow @@Res = round(R)@@ @@ Unit = "Omega" @@ \\
\end{align*}