1) sin(a-b)+cos a*sin b =sina*cosb - cosa*sin b+cos a*sin b=sin a*cos b
2) cos(пи/2 - t)*ctg(-t)/sin (пи/2+t) = - sin t *ctg t/cos t =(-sint*cost/sint)/cost =
= -cost/cost = -1
3) ctg(-t)*sin t +cos(пи + t)=-cost/sint*sin t -cost =-cost-cost=-2cost
