cos(3п/2+x)cos3x-cos(п-x)sin3x=-1

task/17942983
--------------------
Cos(3п/2+x)cos3x-cos(п-x)sin3x=-1
--------
cos(3π/2+x)cos3x - cos(π-x)sin3x = -1 ;
* * *cos(3π/2+x) =sinx ; cos(π-x) = - cosx  формулы приведения * * * 
sinx*cos3x +cosx*sin3x = -1 ;
sin(3x +x) = -1 ;
sin4x  = -1 ;
4x  = -π/2 + 2πn , n∈Z ;
x  = - π/8 + (π/2)*n , n∈Z.