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>
So each dimention is 32 by 8 by 10
so the surface area=2 times(8 times 10)+(2 times (32 times 10))+(2 times (8 times 32))=2 times 80+2 times 320+2 times 256=1312
if halved
just divide each by 2
(2 times 4 times 5)+(2 times 16 times 5)+(2 times 4 times 16)=(2 times 20)+(2 times 80)+(2 times 64)=40+160+128=328
the new surface area is 328 mm^2
(x² + 16)(x² - 16)
= (x²)² - 16²
= x⁴ - 256
