1−x21+x2\frac{1-x^{2}}{1+x^{2}}1+x21−x2
2x1+x2\frac{2 x}{1+x^{2}}1+x22x
x21+x2\frac{x^{2}}{1+x^{2}}1+x2x2
1−x1+x2\frac{1-x}{1+x^{2}}1+x21−x