`cos 3x + sqrt{3}sin 3x = sin x + sqrt{3}cos x`
`<=> 1/(2)cos 3x + (\sqrt{3})/(2)sin 3x = 1/(2)sin x + (\sqrt{3})/(2)cos x`
`<=> sin (π/3 + 3x) = sin (x + π/3)`
`<=>` \(\left[ \begin{array}{l}\dfrac{π}{3} + 3x = x + \dfrac{π}{3} + k2π\\\dfrac{π}{3} + 3x = \dfrac{2π}{3} - x + k2π\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x = k\pi\\x = \dfrac{π}{12} + k\dfrac{π}{2}\end{array} \right.\) `(k ∈ ZZ)`
