[docs] notation enhancement: introduced parallel operator

documentation/chap/hardware/voltage_divider.tex

@@ -42,7 +42,7 @@ \section{Voltage Divider}
 
 We can use this circuit to reduce a voltage but its usability as a voltage source is limited. This can be shown in \cref{fig:loaded-voltage-divider} by adding a load, in this case a resistor $R_L$. Now the total resistance of the parallel resistors $R_2$ and $R_L$ calculates to
 \begin{equation*}
-	R_x = \frac{1}{\frac{1}{R_2} + \frac{1}{R_L}}
+	R_x = R_2 \parallel R_L = \frac{1}{\frac{1}{R_2} + \frac{1}{R_L}}
 \end{equation*}
 and the result of this is smaller than $R_2$ and $R_L$. The load changes the voltage divider and this changes the output voltage $U_o$.