Решить cos8x - cos6x + cos2x - cos4x = 0 - вопрос №525575186240 от zzzzzzz03 27.06.2021 05:11

Question

Алгебра: Решить cos8x - cos6x + cos2x - cos4x = 0

zzzzzzz03 · Answer

(cos8x +cos2x)-(cos6x+cos4x) = 02cos(10x/2)cos(6x/2) - 2cos(10x/2)cos(2x/2) =02cos5xcos3x - 2cos5xcosx=02cos5x(cos3x - cosx) = 02cos5x * 2sinxsin2x=0cos5xsin2xsinx=0cos5x = 0 или     sin2x = 0 или sinx = 05x=π/2 + πn       2x = πk          x=πmx=π/10 + πn/5    x=πk/2 ...