float coth(float x, float epsilon)
{
   float last_n = x/3;
   float sum = last_n;
   float n = 0;

   for(int i = 2; i<=12, i++)
   {
       n = ((-1)^(i+1)*2^(2i))/faculty(2*n) * bernoulli[i] * x^(2*n-1)
       sum += n;
       if((n - last_n) > epsilon))
           return sum;

   }
   return sum;
}