1.2
0,5*0,5-√3*√3/2=1/4-3/2=(1-6)/4=-5/4=-1,25
1.5
2*1/4-3/4+1/√3*1/√3=-1/4+1/3=(-3+4)/12=1/12
2.2
cos²t=1:(1+tg²t)=1:(1+225/64)=1:289/64=64/289
cost=-8/17
sint=-√(1-cos²t)=-√(1-64/289)=-√(225/289)=-15/17
ctgt=1/tgt=8/15
3.1
1-sin²t=cos²t cos²t=cos²t
4.1
cost-sintcost/sint=cost-cost=0
4.2
(1-sin²t)/(1-sint)=(1-sint)(1+sint)/(1-sint)=1+sint