Предмет: Алгебра, автор: maa

cos3x+cos9x=0

Ответы

Автор ответа: Fedor

cos3x+cos9x=2cos((9x+3x)/2)*cos((9x-3x)/2)=2cos(6x)*cos(3x)=0

a) 6x=pi/2+pi*n

x=pi/12+pi*n/6

б) 3x=pi/2+pi*n

x=pi/6+pi*n/3

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