Determine the Internal Angles of a Polygon Programmatically

[Centauri Soldier]

As the title states, I'm trying (with limited success) to determine the internal angels of any polygon given the vertices; however, I'm not getting back the correct the numbers and I'm posting here to see if anyone can see something wrong that I don't.

I'm using a method in my line class called getTheta() to find the angle of the line to the positive x-axis. I've posted the code that determines the theta of a line, below, as well as the updateAngles() function for the polygon class.

Theta Code

tProt.theta = math.deg(math.atan2(oEnd.y, oEnd.x));
--make sure the value is positive
tProt.theta = tProt.theta >= 0 and tProt.theta or 360 + tProt.theta;

updateAngles()

local function updateAngles(tProt)
  tProt.interiorAngles = {};
  tProt.exteriorAngles = {};
  local tEdges = tProt.edges;

  for nLine = 1, tProt.edgesCount do --use the number of vertices since it's the same as the number of edges
    local bIsFirstLine = nLine == 1;
    --local bIsLastLine = nLine == tProt.edgesCount;

    --determine the lines between which the angle will be
    local oLine1 = tEdges[nLine];
    local nLine2Index = bIsFirstLine and (tProt.edgesCount) or nLine - 1;
    local oLine2 = tEdges[nLine2Index];

    ---LEFT OFF HERE

    --get the lines' theta value
    local nTheta1 = oLine1:getTheta();
    local nTheta2 = oLine2:getTheta();
    print("(before) "..nLine.."-> "..nTheta1.." | "..nLine2Index.."-> "..nTheta2);

    --if this is the last line, determine the second theta by flipping it so it's oriented correctly
    if (bIsFirstLine) then
      nTheta2 = (nTheta2 >= 180) and nTheta2 - 180 or nTheta2 + 180;
    end

    print("(after) "..nLine.."-> "..nTheta1.." | "..nLine2Index.."-> "..nTheta2);
    --get the interior angle
  
    --tProt.interiorAngles[nLine] = math.max(nTheta1, nTheta2) - math.min(nTheta1, nTheta2);
    local nSmall = math.min(nTheta1, nTheta2);
    local nLarge = math.max(nTheta1, nTheta2);

    tProt.interiorAngles[nLine] = nLarge;
    print(tProt.interiorAngles[nLine])
  
     --get the exterior angle: this allows for negative interior angles so all extangles == 360 even on concave polygons
    tProt.exteriorAngles[nLine] = 180 - tProt.interiorAngles[nLine];
  end

end

Any help would be most appreciated