[tex]Unghiurile~~x ~si~( \frac{\pi}{2} -x)~sunt~complementare~deoarece: \\ x +(\frac{\pi}{2} -x)=x + \frac{\pi}{2} -x = \frac{\pi}{2} \\ \\ =\ \textgreater \ ~~ctg(\frac{\pi}{2} -x) = tg\,x \\ \\ =\ \textgreater \ ~~Ecuatia: \\ tg\,x=ctg(\frac{\pi}{2} -x) \\ este~echivalenta~cu~ecuatia: \\ tg\,x=tg\,x \\ =\ \textgreater \ ~~x~pate~lua~orice~valoare. \\ R: \boxed{x\in R}[/tex]
