Ответ №1
(cos8x +cos2x)-(cos6x+cos4x) = 0
2cos(10x/2)cos(6x/2) - 2cos(10x/2)cos(2x/2) =0
2cos5xcos3x - 2cos5xcosx=0
2cos5x(cos3x - cosx) = 0
2cos5x * 2sinxsin2x=0
cos5xsin2xsinx=0
cos5x = 0 или sin2x = 0 или sinx = 0
5x=π/2 + πn 2x = πk x=πm
x=π/10 + πn/5 x=πk/2
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