f(x) = 4.8x
Have to calculate the apothem of the octagon.
That is the altitude of one of the triangles whose base is x and vertex angle is 22.5 degrees. Divide 360 degrees /8 = 45 degrees, then divide by 2 for the altitude angle.
Using the apothem "a" formula for the area,
Area = a^2 P/2 where P is the perimeter which is 8x
Tan 22.5 = (x/2)/a. a = 1.2
