Людии помогите срочно 10-11 класс

1 sin²t/(1+cost)+sint*ctgt=(1-cos²t)/(1+cost)+sint*cost/sint= =(1-cost)(1+cost)/(1+cost+sint=1-cost+cost=1 1=1 2 sint=-15/17 cost=-√(1-sin²t)=-√(1-225/289)=-√(64/289)=-8/17 tgt=sint/cost=-15/17:(-8/17)=15/17*17/8=15/8 ctgt=1/tgt=1:15/8=8/15 1 a)(cos(720+60)-ctg(540-45))*sin(180+45)=(cos60-ctg(-45))*(-sin45)= =(1/2+1)*(-√2/2=-3√2/4 b)sin(-23π/4)*tg19π/6=-sin(6π-π/4)*tg(3π+π/6)=-sin(-π/4)*tgπ/6= =√2/2*√3/3=√6/6 2 2cos(3π/2+a)/sin(π+a)=2sina/(-sina)=-1