Giúp mình với thanks nhiều

Đáp án + Giải thích các bước giải:

`1.`

`sin2x=sin\frac{2pi}{7}`

`<=>`\(\left[ \begin{array}{l}2x=\dfrac{2\pi}{7}+k2\pi\\2x=\pi-\dfrac{2\pi}{7}+k2\pi\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=\dfrac{\pi}{7}+k\pi\\2x=\dfrac{5\pi}{7}+k2\pi\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=\dfrac{\pi}{7}+k\pi\\x=\dfrac{5\pi}{14}+k\pi\end{array} \right.\)`(kinZZ)`

`2.`

`sin3x-sinx=0`

`<=>sin3x=sinx`

`<=>`\(\left[ \begin{array}{l}3x=x+k2\pi\\3x=\pi-x+k2\pi\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}2x=k2\pi\\4x=\pi+k2\pi\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=k\pi\\x=\dfrac{\pi}{4}+\dfrac{k\pi}{2}\end{array} \right.\)`(kinZZ)`

`3.`

`sin5x+sin2x=0`

`<=>sin5x=-sin2x`

`<=>sin5x=sin(-2x)`

`<=>`\(\left[ \begin{array}{l}5x=-2x+k2\pi\\5x=\pi+2x+k2\pi\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}7x=k2\pi\\3x=\pi+k2\pi\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=\dfrac{k2\pi}{7}\\x=\dfrac{\pi}{3}+\dfrac{k2\pi}{3}\end{array} \right.\)`(kinZZ)`