Cos x + cos 2x = 2sin x

Question

Cos x + cos 2x = 2sin x

Answer 1

1-2sin²x-2sinx-1=0
-2sinx(sinx+1)=0
sinx=0⇒x=πn
sinx=-1⇒x=-π/2+2πn

Comments

куда косинус дели?

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косинус х