Finding the area of a circumscribed polygon

Watch this video and you will know how to find the area of circumscribed polygon, no matter regular or irregular. In this video, I prove, that the area of the circumscribed polygon is equal to the half of its perimeter multiplied by the radius of its incircle (inscribed circle). You can use this formula for any kind of the polygon is it has the inscribed circle (the circle which is to all of the sides of the polygon).