Sin3π/7Cosπ/14 + Cos3π/7Sinπ/14 = Sin(3π/7 + π/14) = Sinπ/2 = 1
Sin3π/8Sinπ/8 - Cos3π/8Cosπ/8 = - (Cos3π/8Cosπ/8 - Sin3π/8Sinπ/8) =
= - Cos(3π/8 + π/8) = - Cosπ/2 = 0
Ответ
2x^2-4x-14=0
x^2-2x-14=0
D=4+56=(2sqr15)^2
x1=(2+2sqr15)÷2=1+sqr15
x2=1-sqr15
2а-3в=16-(-9)=24 3а-в=24-(-3)=27 24<27
X²-49<-40
x²<9
x²=9
x₁=3
x₂=-3
Дальше во вложениях.
Ответ: (-3;3)