Isosceles trapezoid

The area of an isosceles trapezoid can be found in another way, if known angle at the base and the radius of the inscribed circle. The fact is that the center of the inscribed circle, from where the radius originates, is located exactly in the center of the trapezoid, thus equalizing the height and diameter of the circle (or doubled radius) we can find the middle line, from here we get the trapezoid area formula.