Question

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$cos600°+cos(x-200°)+sin(x+250°)=sin870°$

Answer 1

cos(720°-120°)+cos(x-180°-20°)+sin(x+180+70°)=sin(720°+150°)

cos(180°-60°)-cos(20-x)-sin(90+(x-20))=sin(180-30)

-cos60-cos(20-x)-cos(x-20)=sin30

-1/2-2cos(x-20)=1/2

2cos(x-20)=-1

cos(x-20)=-1/2

x-20=П+-П/3+2Пk

20°=П/9

x=П+П/9+-П/3+2Пk

x1=-5П/9+2Пk

x2=7П/9+2Пk