sin in bash

function sin()
{
  if [ $# != 2 ]
  then
    echo "FAIL" >&2
    return 2
  fi

  result=$1
  x=$1
  n=1
  fact=1
  for k in `seq 2 $2`
  do
    x=$(( $x * $1 * $1 ))
    n=$(( $n + 2 ))
    fact=$(( (-1.0) * $fact * ($n - 1) * $n ))
    result=$(( $result + $x / $fact ))
  done
  echo $result
}