Задача 16888 Решите пожалуйста №8.089...
Условие
математика 10-11 класс
817
Решение
★
=(sin^2(π/10)-cos^2(π/10))/(sin(π/10)·cos(π/10))=
=-cos(2π/10)/(sin(π/10)·cos(π/10))=
=-2cos(π/5)/(2sin(π/10)·cos(π/10))=
=-2cos(π/5)/(sin(2π/10))
-2ctg(π/5)
-2ctg(π/5)/ctg^2(π/5)=-2/ctg(π/5)