Each of the nine sides is of length 144/9=16 in. and subtends an angle of 40°of the circumference of its circumscribed circle.
If you connect the center of the circumscribed circle to each end of the sides of the polygon, you get 9 triangles
The altitude of each is 8cot20º, the area is 1/2(16)(8cot20º)=64cot20º. The total area of the polygon is 9 time this, or 576cot20°=1582.546994
