Question

Доказать тождество...

Answer 1

(cos4x+cos3x+cos2x)/(sin4x+sin3x+sin2x)=

(2cos3x*cosx+cos3x)/(2(sin3x*cosx+sin3x)=

cos3x*(2cosx+1)/(sin3x*(2cosx+1))=cos3x/(sin3x)=ctg3x

Доказано.