Giúp mik vs mik đang cần gấp, mik cảm ơn

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Giúp mik vs mik đang cần gấp, mik cảm ơn
giup-mik-vs-mik-dang-can-gap-mik-cam-on

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Gerda 6 years 2020-10-24T06:44:00+00:00 1 Answers 122 views 0

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  1. Maris
    0
    2020-10-24T06:45:28+00:00
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    `sin^2 x+ sin^2 2x = 0`

    `<=> (1-cos2x) + (1-cos4x) =0`

    <=> cos2x + cos4x = 2`

    `<=> cos2x + 2cos^2 2x – 1 – 2 =0`

    `<=> 2cos^2 2x + cos2x – 3 =0`

    `<=>` \(\left[ \begin{array}{l}cos2x=1\\cos2x=\dfrac{-3}{2} (L)\end{array} \right.\) 

    `<=> 2x = k2π`

    `<=> x =kπ`

    Vậy `x= kπ (k \in \mathbbZ)`

    .

    `cos 2x + cos 4x = 2`

    `<=> cos2x + 2cos^2 2x – 1 – 2=0`

    `<=> 2cos^2 2x + cos2x – 3 =0`

    `<=>….`

    `<=> x=kπ `

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