Log3(x-1)+2log9(17+x)=7+log1/3 9 ))

log₃(x-1)+log₉(17+x)²=7-log₃9          

log₃(x-1)+log₃(17+x)=7-2

x-1+17+x=5

2x=-11

x=-5,5

1) tg(180-a): сtg(90-a)=-tga: tga=-1

2)cos(90-a)-1: cos(180-a)=sina-1: (-cosa)=-(sina-1): cosa=1-sina: сosa