1
sina=-4/5,a-3ч
cosa=-√(1-sin²a)=-√(1-16/25)=-√(9/25)=-3/5
tga=sina/cosa=-4/5:(-3/5)=4/5*5/3=4/3
ctga=1/tga=1:4/3=3/4
2
(sina/cosa+cosa/sina)*sina=(sin²a+cos²a)/(sinacosa)* sina=
=1/(sinacosa) *sina=1/cosa
cosa=-0,6
1/(-0,6)=-10/6=-5/3
3
(tga+1)(-ctga+1)/[-ctga+1)(ctga+1)]=(tga+1)*(-1/tga +1)/[-tga+1)(1/tga+1)=
=(tga+1)(-1+tga)/[(-tga+1)*(1+tga)]=-1