Math & Shapes & Points

I need to figure out if a point is within a given polygon, by points.

From what iv researched, you can figure this out by doing some angle math.
However I havent been able to get this to work correctly.

Anyone know what I'm doing wrong?

list  positions =[
<51.47958, 35.27858, 80.32906>,
<51.47958, 35.27858, 83.15882>,
<51.47958, 48.38833, 80.32906>,
<51.47958, 48.38833, 83.15882>,
<60.99294, 48.42350, 80.32906>,
<60.99294, 48.42350, 83.15882>,
<60.99294, 35.27858, 80.32906>,
<60.99294, 35.27858, 83.15882>
];
vector target =  <61.62799, 42.75370, 81.86267>;

float EPSILON = 0.0000001;

float MODULUS(vector p){
     return llSqrt(p.x*p.x + p.y*p.y + p.z*p.z);
    }

float CalcAngleSum(vector point){
    integer i;
    integer n = llGetListLength(positions);
    float m1;
    float m2;
    float anglesum=0;
    float costheta;
    vector p1;
    vector p2;
    for (i=0;i<n;i++) {
      vector p = llList2Vector(positions,i);
      p1.x = p.x - point.x;
      p1.y = p.y - point.y;
      p1.z = p.z - point.z;
      vector pp = llList2Vector(positions,(i+1)%n);
      p2.x = pp.x - point.x;
      p2.y = pp.y - point.y;
      p2.z = pp.z - point.z;

      m1 = MODULUS(p1);
      m2 = MODULUS(p2);
      if (m1*m2 <= EPSILON)
         return(TWO_PI); 
      else
         costheta = (p1.x*p2.x + p1.y*p2.y + p1.z*p2.z) / (m1*m2);

      anglesum += llAcos(costheta);
   }
   return anglesum;
}

Does it work if the test 'Target' is INSIDE the space?

the results are wrong regardless if its inside the space or out.