First symmetrically cut the octagon to get 8 pieces. (So that you will get the idea that this polygon is divided into 8 triangles)
Then find the area of one of the triangles:
Area of Triangle =
A = × 12 × 19
A = 114 cm²
To find the area of the whole octagon shape:
A = 114 × 8 = 912 cm²
<em>Hope it helps!</em>
