Area of the polygon with   equal sides is .

Divide the polygon into  congruent triangles with central angle .

The polygon is inscribed in circle with radius .

Therefore, two sides of the triangle have equal length of .

Determine area of the each triangle.

Area of each triangle is .

Here  and .

Total polygon area is  times the area of the single triangle.

.

(b) Find .

.

Assume .

As  , then .

.

Property of limit function: .

(a) .

(b) .