Sin 4x = $\sqrt{2}$/2
=> Sin 4x = sin(π/4)
=> \(\left[ \begin{array}{l}4x = π/4 + k2π\\4x = π - π/4 + k2π\end{array} \right.\) (k ∈ Z)
=> \(\left[ \begin{array}{l}x = (π/4 + k2π)/4\\x = (3π/4 + k2π)/4\end{array} \right.\) (k ∈ Z)
=> \(\left[ \begin{array}{l}x = π/16 + kπ/2\\x = 3π/16 + kπ/2\end{array} \right.\) (k ∈ Z)
Vậy nghiệm của PT đã cho là:
S = {π/16 + kπ/2; 3π/16 + kπ/2}, k ∈ Z.
