Lua: Circle API

pi = math.pi

function inscribedPoly(_radius,_sides,_units)
  local _angle = (math.pi * (_sides - 2)) / (2 * _sides)
  local _height = math.sin(_angle) * _radius
  local _baseRight = math.cos(_angle) * _radius
  local _area = _height * _baseRight * _sides
  if _units then
    print(_area.." "..tostring(_units).."^2")
  end
  return _area
end

function circumscribedPoly(_radius,_sides,_units)
  local _angle = (math.pi * (_sides - 2)) / (2 * _sides)
  local _height = _radius
  local _baseRight = _height / math.tan(_angle)
  local _area = _height * _baseRight * _sides
  if _units then
    print(_area.." "..tostring(_units).."^2")
  end
  return _area
end

function sidePoly(_sides,_length,_units)
   local _angle = (math.pi * (_sides - 2)) / (2 * _sides)
   local _baseRight = _length / 2
   local _height = _baseRight * math.tan(_angle)
   local _area = _height * _baseRight * _sides
   if _units then
       print(_area.." "..tostring(_units).."^2")
    end
    return _area
end

function area(_radius) return math.pi * (_radius ^ 2) end

function circumference(_radius) return math.pi * _radius * 2 end

function diameter(_radius) return _radius * 2 end

function sphereVolume(_radius) return math.pi * (_radius ^ 3) * (4/3) end