To find the average current of a trapezium, calculate the total area under the curve during one period and divide it by the period. The area of a trapezium can be determined using the formula A = (a + b) * h / 2, where 'a' and 'b' are the lengths of the parallel sides and 'h' is the height. In this context, the formula can be adapted to (I_min + I_max) * t_on / 2. Understanding these calculations is essential for accurately determining average current. This method effectively simplifies the process of finding average current in trapezoidal waveforms.