First let's remember that a regular octahedron is solid with 8 faces all of them equilateral triangles, so if we find the area for each face we know that is just finding the area of an equilateral triangle:
And if we want to know the surface area of all the figures we just need to multiply the area of one equilateral triangle by 8 because there are 8 faces, and as you can see the value a is the value of each edge so, let's do it:
The length of each edge is 8 ft
