Electric Field of an n sided polygon

[lao]

We have an n sided polygon, each side is length 2L and R is the distance from the center of the polygon to the mid-point of any side. We know, L=Rtan(pi/n).

I need: "the E-field on the axis of the polygon at a point distance h above it"

When n goes to infinity, we should get the same E-field as a uniform ring charge:
E= kQh/(h^2+R^2)^1.5

any help would be awesome, thx :)

[Tide]

And, what have you done so far to solve the problem?

[rachmaninoff]

Simple: do we have any symmetry here? Find the field to a single side (a finite line segment).

Hope this helps.