Tga и cosa, если ctga= -5/12 и 3П/2

Question

Tga и cosa, если ctga= -5/12 и 3П/2

Answer 1

Tga=1/ctga
tga=-12/5
cos²a=1:(1+tg²a)=1:(1+144/25)=1:169/25=25/169
cosa=5/13?a в 4ч