Вычыслить 1)tg -210°; 2)ctg 5п/3; 3)sin 870°; 4)cos(-8п/3).

1 tg-210=-tg(180+30)=-tg30=/3
2 ctg5p/3=ctg((6p-p)/3)=ctg(2p-p/3)=ctg(-p/3)=-/3
3 sin870=sin(360*2+150)=sin(150)=sin(180-30)=sin30=1/2
4 cos(-8p/3)=cos((6p+2p)/3)=cos(2p+2p/3)=cos2p/3=cos120=cos(90+30)=-/3