Answer:
Area of a regular polygon formulas
Step-by-step explanation:
area = n * a * ri / 2 , having ri - incircle radius (it's also an apothem - a line segment from the center to the midpoint of one of its sides)
area = perimeter * ri / 2 , given ri and polygon perimeter.
area = n * (ri)² * tan(π/n) , given ri.
