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

Toán Lớp 11: cho em hỏi câu này làm sao ạ cos(2x+ π/6) = 1/4

Toán Lớp 11: cho em hỏi câu này làm sao ạ
cos(2x+ π/6) = 1/4

Comments ( 1 )

  1. Giải đáp + Lời giải và giải thích chi tiết:
    cos(2x+ π/6) = 1/4
    <=>\(\left[ \begin{array}{l}2x+\dfrac{\pi}{6}=\arccos(\dfrac{1}{4})+k2\pi\\2x+\dfrac{\pi}{6}=-\arccos(\dfrac{1}{4})+k2\pi\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}2x=-\dfrac{\pi}{6}+\arccos(\dfrac{1}{4})+k2\pi\\2x=-\dfrac{\pi}{6}-\arccos(\dfrac{1}{4})+k2\pi\end{array} \right.\)
    <=>\(\left[ \begin{array}{l}x=-\dfrac{\pi}{12}+\dfrac{1}{2}\arccos(\dfrac{1}{4})+k\pi\\x=-\dfrac{\pi}{12}-\dfrac{1}{2}\arccos(\dfrac{1}{4})+k\pi\end{array} \right.\)(kinZZ)

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