The functions may be approximated as:

A (x) \approx x - \frac{x^{3}}{3!} B (x) \approx \frac{x^{2}}{2!} - \frac{x^{4}}{4!} C (x) \approx x - \frac{x^{2}}{2} D (x) \approx x + x^{2}