code: function(x) {
      var limit = Math.PI/4;
      if (x < -limit || x > limit) {
        return (Math.cos(x) - 1.0);
      }
  
      var xx = x * x;
      return xx *
        (-0.5 + xx *
          (1/24 + xx *
            (-1/720 + xx *
              (1/40320 + xx *
                (-1/3628800 + xx *
                  (1/4790014600 + xx *
                    (-1/87178291200 + xx *
                      (1/20922789888000)
                    )
                  )
                )
              )
            )
          )
        )
    }
docs: Calculates cos(x) - 1 using Taylor series if x is small.
  
  @param {number} x
  @returns {number} cos(x) - 1