Đáp án:
\(S = \left\{\dfrac{\pi}{3} + k\pi;\ -\dfrac{\pi}{3} + k\pi\ \Bigg|\ k\in\Bbb Z\right\}\)
Giải thích các bước giải:
\(\begin{array}{l}
\quad \sin^2x - \dfrac34 = 0\\
\Leftrightarrow \dfrac{1 - \cos2x}{2} - \dfrac34 = 0\\
\Leftrightarrow \cos2x = -\dfrac12\\
\Leftrightarrow \left[\begin{array}{l}2x =\dfrac{2\pi}{3} + k2\pi\\2x = - \dfrac{2\pi}{3} + k2\pi\end{array}\right.\\
\Leftrightarrow \left[\begin{array}{l}x = \dfrac{\pi}{3} + k\pi\\x = -\dfrac{\pi}{3} + k\pi\end{array}\right.\quad (k\in\Bbb Z)\\
\text{Vậy}\ S = \left\{\dfrac{\pi}{3} + k\pi;\ -\dfrac{\pi}{3} + k\pi\ \Bigg|\ k\in\Bbb Z\right\}
\end{array}\)
