Đáp án:
\(\left[ \begin{array}{l}x=-\dfrac{\pi}6+k2\pi\\x=-\dfrac{\pi}2+k2\pi\end{array} \right.\)
Giải thích các bước:
\(\cos(x+60^{\circ})=\dfrac{\sqrt 3}{2}\)
\(\to \cos(x+\dfrac{\pi}3)=\cos \dfrac{\pi}6\)
\(\to\) \(\left[ \begin{array}{l}x+\dfrac{\pi}3=\dfrac{\pi}6+k2\pi\\x+\dfrac{\pi}3=-\dfrac{\pi}6+k2\pi\end{array} \right.\)
\(\to\left[ \begin{array}{l}x=-\dfrac{\pi}6+k2\pi\\x=-\dfrac{\pi}2+k2\pi\end{array} \right.\)
