Решите пожалуйста №8.082
sin(2π/7)=2sin(π/7)*cos(π/7) tg(π/7)+ctg(π/7)=(sin(π/7)/cos(π/7))+(cos(π/7)/sin(π/7)= =(sin^2(π/7)+cos^2(π/7))/(sin(π/7)*cos(π/7))= =1/(sin(π/7)*cos(π/7)) sin(2π/7)*(tg(π/7)+ctg(π/7))=2 1+cos(π/7)=2cos^2(π/14) О т в е т. 1