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

Toán Lớp 11: h) 2cos^2 (5x) – 2sin 5x + 2 = 0 cám ơn trc

Home/ Toán Lớp 11: h) 2cos^2 (5x) – 2sin 5x + 2 = 0 cám ơn trc

Toán Lớp 11: h) 2cos^2 (5x) – 2sin 5x + 2 = 0 cám ơn trc

Tháng Bảy 21, 2022 Toán học 2 Comments 0 views

Toán Lớp 11: h) 2cos^2 (5x) – 2sin 5x + 2 = 0 cám ơn trc

Comments ( 2 )

  1. truongthanhhung
    truongthanhhung
    21 Tháng Bảy, 2022 at 4:41 chiều
    Reply
    2cos^2 5x – 2sin 5x + 2 = 0
    ⇔2(1-sin²5x ) – 2sin 5x + 2 = 0
    ⇔ 2-2sin²5x – 2sin5x + 2 =0
    ⇔-2sin²5x-2sin5x+4=0
    ⇔ $\left[\begin{matrix} sin5x=1\\ sin5x=-2 (VN)\end{matrix}\right.$
    ⇔ 5x = π/2 + k2π
    ⇔x=π/10 + k(2π)/5  (k∈Z)

  2. cattien
    cattien
    21 Tháng Bảy, 2022 at 4:41 chiều
    Reply
    2cos^2 5x – 2sin 5x + 2 = 0
    <=> 1 + cos^2 5x – sin5x = 0
    <=> 2 – sin^2 5x- sin5 x  = 0
    <=> -sin^2 5x +sin5x – 2sin5x+2=0
    <=>(sin5 x – 1) (sin5 x + 2) = 0
    <=> [(sin5x-1=0),(sin5x+2=0):}
    <=>[(sin5x=1),(sin5x=-2\ \ \ \ \ \ text{(loại)}):} 
    <=> 5 x = pi/2+k2pi
    Vậy S={ pi/10+(k2pi)/5|kinZZ}

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

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