Task/17942983
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Cos(3п/2+x)cos3x-cos(п-x)sin3x=-1
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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.