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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 11: giải phương trình lượng giác sinxcosx= 1/4

Toán Lớp 11: giải phương trình lượng giác
sinxcosx= 1/4

Comments ( 1 )

  1. $sinxcosx=\dfrac{1}{4}$
    $⇔ \dfrac{1}{2}sin2x=\dfrac{1}{4}$
    $⇔ sin2x=\dfrac{1}{2}$
    $⇔ sin2x=sin\dfrac{\pi}{6}$
    $⇔ \left[ \begin{array}{l}2x=\dfrac{\pi}{6}+k2\pi\\2x=\dfrac{5\pi}{6}+k2\pi\end{array} \right.$
    $⇔ \left[ \begin{array}{l}x=\dfrac{\pi}{12}+k\pi\\x=\dfrac{5\pi}{12}+k\pi\end{array} \right.$ $(k∈Z)$
     

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222-9+11+12:2*14+14 = ? ( )