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 10: Giải phương trình: a) cos(x-1)=2/3 b) cos3x=cos12độ c) cos² 2x=1/4 →

Tháng Một 19, 2023 Toán học 1 Comment 0 views

Toán Lớp 10: Giải phương trình:
a) cos(x-1)=2/3
b) cos3x=cos12độ
c) cos² 2x=1/4 →

Comments ( 1 )

  1. diemmyhoa
    diemmyhoa
    19 Tháng Một, 2023 at 11:02 chiều
    Reply
    $a)cos(x-1)=\dfrac{2}{3}$ 
    $⇔$\(\left[ \begin{array}{l}x-1=arccos(\dfrac{2}{3})+k2\pi\\x-1=-arccos(\dfrac{2}{3})+k2\pi\end{array} \right.\) 
    $⇔$\(\left[ \begin{array}{l}x=1+arccos(\dfrac{2}{3})+k2\pi\\x=1+-arccos(\dfrac{2}{3})+k2\pi\end{array} \right.\) 
    $b)cos3x=cos12^o$
    $⇔$\(\left[ \begin{array}{l}3x=12^o+k360^o\\3x=-12^o+k360^o\end{array} \right.\) 
    $⇔$\(\left[ \begin{array}{l}x=4^o+k120^o\\x=-4^o+k120^o\end{array} \right.\) 
    $c)cos^22x=\dfrac{1}{4}$
    $cos2x=cos(\dfrac{\pi}{3})$ hay $cos2x=cos(\dfrac{2\pi}{3})$ 
    $⇔$\(\left[ \begin{array}{l}2x=±\dfrac{\pi}{3}+k2\pi\\2x=±\dfrac{2\pi}{3}+k2\pi\end{array} \right.\) 
    $⇔$\(\left[ \begin{array}{l}x=±\dfrac{\pi}{6}+k\pi\\2x=±\dfrac{\pi}{3}+k\pi\end{array} \right.\) 

Leave a reply

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

Cát Linh

About Cát Linh