Verified answer

[tex]\displaystyle\bf\\1)\\\\Ctg0,6\pi =Ctg\Big(\frac{\pi }{2} +\frac{\pi }{10} \Big)=-tg\frac{\pi }{10} \\\\\\2)\\\\tg\frac{9}{8} \pi =tg\Big(\pi +\frac{\pi }{8} \Big)=tg\frac{\pi }{8}[/tex]