This equation defines the area of a regular polygon, where input a is the apothem and input n is the number of sides:

A=4(`a^2`)*tan(`pi`/n)

Notes

In case future edits cause failure to the equation, here is the original:

(a^2)*n*tan(180/n)

I've tested it and I know it works.

However, there has been an issue concerning degrees/ radians. This equation is suited for degrees and it has been modified to work using radians.