- Sai từ bước 2.
`sin2x = sin (π/2-x)`
`<=>` \(\left[ \begin{array}{l}2x=\dfrac{π}{2}-x+k2π\\2x=π-\dfrac{π}{2}+x+k2π\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}3x=\dfrac{π}{2}+k2π\\x=\dfrac{π}{2}+k2π\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=\dfrac{π}{6}+k\dfrac{2π}{3}\\x=\dfrac{π}{2}+k2π\end{array} \right.\) `(k \in \mathbbZ)`
Vậy PT có 2 họ nghiệm như trên.
