Question

Which function can be used to compute the approximate area, in square inches, of a stop sign if it has a side length of x inches? f(x) = 4.8x2 f(x) = 4x2 f(x) = (4.8)x f(x) = (4)x

Answer 1

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