1
sinx=-40/41
cosx=-√(1-sin²x)=-√(1-1600/1681)=-√(81/1681)=-9/41
tga=sina/cosa=-40/41:(-9/41)=40/41*41/9=40/9
ctga=1/tga=1:40/9=9/40
2
cosx=-21/29
sina=√(1-cos²x)=√1-441/841)=√(400/841)=20/29
tga=sina/cosa=20/29:(-21/29)=-20/29*29/21=20/21
ctga=1/tga=1:20/21=21/20
3
sin(π/9-6x)=cos(6x+7π/18)
cos(6x+7π/18)=-√3/2
6x+7π/18=-5π/6+2πk U 6x+7π/18=5π/6+2πk
6x=-5π/6-7π/18+2πk U 6x=5π/6-7π/18+2πk
6x=11π/9+2πk U 6x=4π/9+2πk
x=11π/54+πl/3 U x=π/27+πk/3,k∈z