A) (sint+cost)²+(sint-cost)²=
= sin²t+2sint*cost+cos²t+sin²t-2sint*cost+cos²t=
= 2sin²t+2cos²t=2(sin²t+cos²t)=2*1=2
б) sint*cost*(tgt+ctgt)²=sint*cost(sint/cost + cost/sint)²=
= sint*cost*((sin²t+cos²t)/sintcost)²=sint*cost(1/sin²t*cos²t)=1/(sintcost)=
=1/(1/2 *(2sint*cost))=2/sin(2t))