`sqrt{3}cos² x + 2sin x.cos x - sqrt{3}sin² x - 1 = 0`
`<=> -sqrt{3}sin² x + 2sin x.cos x + sqrt{3}cos² x = 1`
- Với `cos x = 0`
`=> -sqrt{3} = 1` (không thoả mãn)
- Với `cos x ne 0`
`=> -sqrt{3}tan² x + 2tan x + sqrt{3} = 1 + tan² x`
`<=> (-sqrt{3} - 1)tan² x + 2tan x + sqrt{3} - 1 = 0`
`<=>` \(\left[ \begin{array}{l}tan x = 1\\tan x = \sqrt{3} - 2\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x = \dfrac{π}{4} + kπ\\x = arctan (\sqrt{3} - 2) + kπ\end{array} \right.\) `(k ∈ ZZ)`
