\(\frac{2*\left(\frac{1+\sqrt{1-y^{2}}}{y}\right)}{1+\left(\frac{1+\sqrt{1-y^{2}}}{y}\right)^{2}} \)
\( \frac{\frac{2}{y} \cdot\left(1+\sqrt{1-y^{2}}\right)}{1+\left(\frac{1+\sqrt{1-y^{2}}}{y}\right)^{2}}= \)
\( \frac{\frac{2}{y} \cdot\left(1+\sqrt{1-y^{2}}\right)}{1+\frac{\left(1+\sqrt{1-y^{2}}\right)^{2}}{y^{2}}}= \)
\( \frac{2 y \cdot\left(1+\sqrt{1-y^{2}}\right)}{\left(y^{2}+\left(1+\sqrt{1-y^{2}}\right)^{2}\right)}= \)
\( \frac{2 y \cdot\left(1+\sqrt{1-y^{2}}\right)}{\left(y^{2}+1+2 \cdot \sqrt{1-y^{2}}+1-y^{2}\right)}= \)
\( \frac{2 y \cdot\left(1+\sqrt{1-y^{2}}\right)}{\left(2+2 \cdot \sqrt{1-y^{2}}\right)}= \)
\( \frac{y \cdot\left(1+\sqrt{1-y^{2}}\right)}{\left(1+\sqrt{1-y^{2}}\right)}=y \)