Cos5x+cos3x=sqrt(2)cosx

Question

Cos5x+cos3x=sqrt(2)cosx

Answer 1

2cos4xcosx-√2cosx=0
√2cosx(√2cos4x-1)=0
cosx=0⇒x=π/2+πn
cos4x=√2/2⇒4x=+-π/4+2πn⇒x=+-π/16+πn/2

Comments

спасибо!