Đáp án: \(\left[ \begin{array}{l}x = \frac{π}{6} - \frac{3}{2} + kπ\\x = -\frac{π}{6} - \frac{3}{2} + kπ\end{array} \right.\) `(k ∈ ZZ)`
Giải thích các bước giải:
`cos (2x + 3) = 1/2`
`<=> cos (2x + 3) = cos ((π)/3) `
`<=>` \(\left[ \begin{array}{l}2x + 3 = \frac{π}{3} + k2π\\2x + 3 = -\frac{π}{3} + k2π\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x = \frac{π}{6} - \frac{3}{2} + kπ\\x = -\frac{π}{6} - \frac{3}{2} + kπ\end{array} \right.\) `(k ∈ ZZ)`
