Ctg(360-2) tg(3пи /2-а) cos20-cos70

Question

Ctg(360-2)
tg(3пи /2-а)
cos20-cos70

Answer 1

1) =ctg(-2)=-ctg2
 2) =ctga
3 ) = -2sin(20+70 /2)*sin(20-70 /2)=-2*sin45*sin(-35)=-2*√2/2 *(-sin35)=
= √2*sin35