Вычисли

а) \(\tg \left(\arcctg\cfrac{13}{17}\right) = \) [ ];

б) \(\ctg \left( \arctg \left( - \cfrac{12}{11} \right) \right)= \) [ ];

в) \(\sin \left( \arctg \left( - \cfrac{8}{15} \right) \right) = \) [ ];

г) \(\cos \left( \arcctg \cfrac{5}{12} \right) = \) [ ].