Register Now

Login

Lost Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

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

Toán Lớp 11: sinx +sin 2x +sin 3x +sin4x =0

Tháng Một 21, 2023 Toán học 1 Comment 0 views

Toán Lớp 11: sinx +sin 2x +sin 3x +sin4x =0

Comments ( 1 )

  1. huyenmi76
    huyenmi76
    21 Tháng Một, 2023 at 12:12 chiều
    Reply
    $\sin 4x+\sin x+\sin2x+\sin3x=0$
    $\to 2\sin\dfrac{5x}{2}.\cos\dfrac{3x}{2}+2\sin\dfrac{5x}{2}\cos\dfrac{x}{2}=0$
    $\to 2\sin\dfrac{5x}{2}\left(\cos\dfrac{3x}{2}+\cos\dfrac{x}{2}\right)=0$
    $\to \sin\dfrac{5x}{2}.2\cos x\cos \dfrac{x}{2}=0$
    $\to \left[ \begin{array}{l}\sin\dfrac{5x}{2}=0 \\ \cos x=0 \\ \cos\dfrac{x}{2}=0 \end{array} \right.$
    $\to$ $\left[ \begin{array}{l}x=\dfrac{k2\pi}{5} \\x=\dfrac{\pi}{2}+k\pi\\ x=\pi+k2\pi \end{array} \right.$ 

Leave a reply

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

Nhân

About Nhân