<span>The nine radii of a regular Nonagon divides into 9 congruent isosceles triangles </span>therefore [the area of <span>a regular nonagon]=9*[area of isosceles triangle]
</span>[area of isosceles triangle]=b*h/2------> 15*20.6/2----> 154.5 cm² so [the area of a regular nonagon]=9*[154.5]------> 1390.5 cm²
