Answer:
This polygon is comprised of 30 congruent triangles, each with a central angle of 12°
And using trig, each has an area of......
(1/2)(20)^2 sin(12°) = 41.5823381636 sq ft
So, 30 times this = 1247.470144908 sq ft = 1247.5 sq ft (rounded to the nearest tenth)