[tex]2\sqrt{3}cos^{2}x + (4-\sqrt{3})cosx - sin2x +sinx -2 =0[/tex]
mấy bạn giải giúp mình với ạh
$\iff [2\sqrt{3}\cos^2 x+(4-\sqrt{3}) \cos x-2]-2\sin x\cos x+\sin x=0$
$\iff (2\cos x-1)(\sqrt{3} \cos x+2)-\sin x(2\cos x-1)=0$
$\iff (2\cos x-1)(\sqrt{3} \cos x-\sin x+2)=0$
$\iff \left[\begin{matrix} \cos x=\dfrac{1}{2} \\ \sqrt{3}\cos x-\sin x=-2 \end{matrix}\right.$
Xét phần dưới:
$\dfrac{\sqrt{3}}{2} \cos x-\dfrac{1}{2} \sin x=-1$
$\iff \sin (\dfrac{\pi}{3}-x)=-1$
$\iff \dfrac{\pi}{3}-x=\dfrac{-pi}{2}+k2\pi$
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