Cos (π/7)*cos(4π/7)*cos(2π/7) равно? - вопрос №577859174727 от sinethu 26.05.2022 16:05

Question

Алгебра: Cos (π/7)*cos(4π/7)*cos(2π/7) равно?

sinethu · Answer

-cos(π/7)*cos(2π/7)*cos(4π/7)==-sin(π/7)*cos(π/7)*cos(2π/7)*cos(4π/7)/sin(π/7)==-sin(2π/7)*cos(2π/7)*cos(4π/7)/[2sin(π/7)]==-sin(4π/7)*cos(4π/7)/[4sin(π/7)]=-sin(8π/7)/[-8sin(π/7)]==-sin(π-π/7)/[8sin(π/7)]=-sin(π/7)/[8sin(π/7)]=-1/8...