Вычисли

а) \(\tg \left(\arcctg\dfrac{12}{13}\right) = \) [ ];

б) \(\ctg \left( \arctg \left( - \dfrac{15}{14} \right) \right)= \) [ ];

в) \(\sin \left( \arctg \left( - \dfrac{4}{3} \right) \right) = \) [ ];

г) \(\cos \left( \arcctg \dfrac{3}{4} \right) = \) [ ].