b.
\(cos\left(\dfrac{x}{2}-60^0\right)=\dfrac{1}{2}\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{x}{2}-60^0=60^0+k360^0\\\dfrac{x}{2}-60^0=-60^0+k360^0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=240^0+k720^0\\x=k720^0\end{matrix}\right.\)
e.
\(\Leftrightarrow sin2x=-cos\left(x+\dfrac{\pi}{3}\right)\)
\(\Leftrightarrow sin2x=sin\left(x+\dfrac{5\pi}{6}\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=x+\dfrac{5\pi}{6}+k2\pi\\2x=\dfrac{\pi}{6}-x+k2\pi\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5\pi}{6}+k2\pi\\x=\dfrac{\pi}{18}+\dfrac{k2\pi}{3}\end{matrix}\right.\)
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