Mọi người giúp mình mấy bài này với ạ :(

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Mọi người giúp mình mấy bài này với ạ 🙁
moi-nguoi-giup-minh-may-bai-nay-voi-a

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Calantha 4 years 2020-10-19T17:32:11+00:00 1 Answers 62 views 0

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  1. Edana
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    2020-10-19T17:33:31+00:00
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    `c)`

    \(\left\{ \begin{array}{l}sin (\dfrac{π}{6} – \dfrac{x}{3}) \ne 0 \\sin 2x – 1 \ne 0\end{array} \right.\)  

    `<=>` \(\left\{ \begin{array}{l}\dfrac{π}{6} – \dfrac{x}{3} \ne kπ\\2x \ne \dfrac{π}{2} + k2π\end{array} \right.\) 

    `<=>` \(\left\{ \begin{array}{l}x \ne \dfrac{π}{2} + k3π\\x \ne \dfrac{π}{4} + kπ\end{array} \right.\) `(k ∈ ZZ)`

    `=> D = RR \\ {π/2 + k3π; π/4 + kπ | k ∈ ZZ}`

    `d)`

    `sin 3x – sin(π/3 – x) ne 0`

    `<=> sin 3x ne sin (π/3 – x)`

    `<=>` \(\left[ \begin{array}{l}3x \ne \dfrac{π}{3} – x + k2π\\3x \ne x – \dfrac{π}{3} + k2π\end{array} \right.\) 

    `<=>` \(\left[ \begin{array}{l}x \ne \dfrac{π}{12} + k\dfrac{π}{4}\\x \ne -\dfrac{π}{6} + kπ\end{array} \right.\) `(k ∈ ZZ)`

    `=> D = RR \\ {π/12 + k(π)/4; -π/6 + kπ | k ∈ ZZ}`

    `e)` 

    `cos (x/2) – cos 3x ne 0`

    `<=> cos (x/2) ne cos 3x`

    `<=> x/2 ne ±3x + k2π`

    `<=> x ne ±6x + k4π`

    `<=>` \(\left[ \begin{array}{l}x \ne k\dfrac{4π}{5}\\x \ne k\dfrac{4π}{7}\end{array} \right.\) 

    `=> D = RR \\ {k(4π)/5; k(4π)/7 | k ∈ ZZ}`

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