A regular decagon has 10 equal sides. An apothem is a perpendicular bisector to the side. This means 2 equal right triangle are formed on each side (20 equal right triangles) or 10 equal isosceles triangles.
Using the 10 equal isosceles triangles and A = .5(base)(height)
Base is a side and height is apothem
Area of regular decagon = 10 × .5 × 8 × 12.3 = 492.0 yd²
Answer: 492.0 yd²
