Раз прося выразить синус через косинус, будем применять одну формулу: Sinα = Cos(π/2 - α)
1) Сosπ/5 и Sinπ/5
Sinπ/5 = Cos(π/2 - π/5) = Cos3π/10
Сosπ/5 = Cos2π/10
Ответ: Сosπ/5 > Sinπ/5
2) Sinπ/7 и Cosπ/7
Sin π/7 = Сos(π/2 - π/7) = Cos5π/14
Cosπ/7 = Cos2π/14
Ответ: Sinπ/7 < Cosπ/7<br>3)Cos3π/8 и Sin5π/8
Sin5π/8 = Cos(π/2 - 5π/8) = Cos(-π/8) = Сosπ/8
Ответ: Cos3π/8 < Sin5π/8<br>4) Sin3π/5 и Cosπ/5
Sin3π/5 = Сos(π/2 - 3π/5) = Cos(-π/10) = Cosπ/10
Сosπ/5 = Cos2π/10
Ответ: Sin3π/5 > Cosπ/5
5)Cosπ/6 и Sin5π/14
Sin5π/14 = Сos(π/2 - 5π/14) = Cos2π/14= Сosπ/7
Ответ: Cosπ/6 < Sin5π/14
6) Cosπ/8 и Sin3π/10
Sin3π/10 = Cos(π/2 - 3π/10) = Cos2π/10 = Cosπ/5
Ответ: Cosπ/8 > Sin3π/10
Знаешь, для удобства: для косинуса
угол больше, сам косинус меньше