Đáp án:
$a){\left[\begin{aligned}x=\dfrac{\pi}{4}+k2\pi\\x=\dfrac{\pi}{4}+\dfrac{k2\pi}{3}\end{aligned}\right.}\\$
Giải thích các bước giải:
$a)
\sin 2x=\sin\left ( x+\dfrac{\pi}{4} \right )\\
\Leftrightarrow {\left[\begin{aligned}2x=x+\dfrac{\pi}{4}+k2\pi\\2x=\pi-x-\dfrac{\pi}{4}+k2\pi\end{aligned}\right.}\\
\Leftrightarrow {\left[\begin{aligned}x=\dfrac{\pi}{4}+k2\pi\\3x=\dfrac{3\pi}{4}+k2\pi\end{aligned}\right.}\\ \Leftrightarrow {\left[\begin{aligned}x=\dfrac{\pi}{4}+k2\pi\\x=\dfrac{\pi}{4}+\dfrac{k2\pi}{3}\end{aligned}\right.}\\$
