1) cos a - ctg a (-sin a) =
2) 2 sin (-pi/6) + 3 + 7,5 tg (-pi) + 1/8 cos 3/2 pi =

1)=cosa+cosa/sina*sina=cosa+cosa=2cosa
2)2*(-1/2)+3+7,5*0+1/8*(-1)=-1+3-1/8=1 7/8