Trapezoid transform to rectangle The area formula for a trapezoid can be written as ¹/₂(base₁+base₂)*h. The average of the bases, ¹/₂(base1+base2), is called the median. So the area can be seen as the median*h, a much simpler rectangular formula. Use the rotation slider to transform by rotation the trapezoid into a rectangle. Adjust the width of the trapezoid by dragging on the corners; this app works when the base2 angles are acute. Adjust the height of the trapezoid by using the slider.