1)sin²a=1:(1+ctg²a)=1:(1+25/144)=1:169/144)=144/169⇒sina=-12/13
cosa=-√1-144/169=-√25/169=-5/13
tga=1/ctga=12/5
2)(sinacosb+cosasinb+sinacosb-cosasinb)/(sinacosb+cosasinb-sinacosb+cosasinb)=2sinacosb/2cosasinb=tgactgb⇒tgactgb=tgactgb
3)Поделим на cos²x≠0
tg²x-6tgx+5=0
a=tgx⇒a²-6a+5=0, a1+a2=6 U a1*a2=5
a1=1,tgx=1⇒x=π/4+πn
a2=5,tgx=5⇒x=arctg5+πn
4)-cos20*_ctg30)=√3cos20
5)-π/4-π/4=-π/2