( toán 11)- phương trình lượng giác.

V

vy000

$3\tan 6x-\dfrac2{\sin 8x}=2\tan 2x-\cot 4x \\ \Leftrightarrow 3\tan(3.2x)-2\tan 2x = \dfrac2{\sin 8x}-\cot 4x \\ \Leftrightarrow 3\tan 2x\dfrac{3-\tan^22x}{1-3\tan^22x}-2\tan 2x=\dfrac2{2\sin4x\cos4x}-\dfrac{\cos 4x}{\sin4x} \\ \Leftrightarrow \tan 2x(\dfrac{9-3\tan^2x}{1-3\tan^22x}-2)=tan 4x \\ \Leftrightarrow \tan 2x(\dfrac{9-3\tan^2x}{1-3\tan^22x}-2)=\dfrac{2\tan 2x}{1-\tan^22x}\\
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