How can we calculate the area of ​​a trapezium using a parallelogram?

The application allows reaching the formula of the area of ​​a trapezium using the construction of a parallelogram with half the height of the trapezium.

What is the relationship between the area of the trapezium [ABCD] and the area of the next parallelogram?

The area of the trapezium is equal to the area of the parallelogram.

What formula do we get for the calculation of the trapezium area?

The height of the parallelogram is half the height \(h\) of the trapezoid. Thus the area of the parallelogram is equal to \((b_1 + b_2) \times {h \over 2}\).
Then the area of the trapezium is given by $$(b_1 + b_2) \times {h \over 2},$$that is, it is equal to the product of the sum of the lengths of the bases by half the height.