Đáp án + Giải thích các bước giải:
`d.`
`sin4x=-sqrt3/2`
`<=>`\(\left[ \begin{array}{l}4x=-\dfrac{\pi}{3}+k2\pi\\4x=\pi+\dfrac{\pi}{3}+k2\pi\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}4x=-\dfrac{\pi}{3}+k2\pi\\4x=\dfrac{4\pi}{3}+k2\pi\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=-\dfrac{\pi}{12}+\dfrac{k\pi}{2}\\x=\dfrac{\pi}{3}+\dfrac{k\pi}{2}\end{array} \right.\)`(kinZZ)`
`e.`
`sin(x+20^o)=sqrt3/2`
`<=>`\(\left[ \begin{array}{l}x+20^o=60^o+k360^o\\x+20^o=180^o-60^o+k360^o\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=40^o+k360^o\\x=100^o+k360^o\end{array} \right.\)`(kinZZ)`
`f.`
`sin(pi/3-x)=-1/4`
`<=>`\(\left[ \begin{array}{l}\dfrac{\pi}{3}-x=\arcsin(-\dfrac{1}{4})+k2\pi\\\dfrac{\pi}{3}-x=\pi-\arcsin(-\dfrac{1}{4})+k2\pi\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=\dfrac{\pi}{3}-\arcsin(-\dfrac{1}{4})-k2\pi\\x=-\dfrac{2\pi}{3}+\arcsin(-\dfrac{1}{4})-k2\pi\end{array} \right.\)`(kinZZ)`
