Đáp án:
\(\left[ \begin{array}{l}x=-\dfrac{7\pi}{6}-k14\pi\\x=\dfrac{7\pi}{2}-k14\pi\end{array} \right.\) `(kinZZ)`
Giải thích các bước giải:
`cos(30^o-x/7)=1/2`
`<=>cos(pi/6-x/7)=cos(pi/3)`
`<=>`\(\left[ \begin{array}{l}\dfrac{\pi}{6}-\dfrac{x}{7}=\dfrac{\pi}{3}+k2\pi\\\dfrac{\pi}{6}-\dfrac{x}{7}=-\dfrac{\pi}{3}+k2\pi\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}-\dfrac{x}{7}=\dfrac{\pi}{6}+k2\pi\\-\dfrac{x}{7}=-\dfrac{\pi}{2}+k2\pi\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=-\dfrac{7\pi}{6}-k14\pi\\x=\dfrac{7\pi}{2}-k14\pi\end{array} \right.\) `(kinZZ)`
