Cos3β-ctg6βsin3β=1/2cos3β
Решение
Cos3β-ctg6βsin3β= Cos3β-cos6β/Sin6β *sin3β=
= (Cos3β*sin6β - cos6β*sin3β)/sin6β=
=sin3β/sin6β = sin3β/2sin3β Cos3β = 1/Cos3β