[tex]\text{Folosim formulele: } \\ \\ tg( \frac{\pi}{2}- \alpha) = ctg\, \alpha \\ \\ ctg\, \alpha = \frac{1}{tg\, \alpha} \\ \\ tg(arctg\;x )=x \\ \\ Rezolvare: \\ \\ tg(\frac{\pi}{2}-arctg \frac{1}{2})=ctg(arctg \frac{1}{2})= \frac{1}{tg(arctg \frac{1}{2})} = \frac{1}{ \frac{1}{2}} =2[/tex]