1. $2\cos3x\cos4x-4\sin^22x + 1 =0$
2. $2cos(\frac{4x}{3})+(sinx + cosx)^2 =0$
1. $2\cos3x\cos4x-4\sin^22x + 1 =0$
2. $2cos(\frac{4x}{3})+(sinx + cosx)^2 =0$
2. $2cos(\frac{4x}{3})+(sinx + cosx)^2 =0$
Ta có :
$\Leftrightarrow 2- 4\times \sin^{2} \frac{2x}{3} + 1 + 2\times \sin x \times \cos x $
$\Leftrightarrow 2- 4\times \sin^{2} \frac{2x}{3} + 1 + -4\sin^{3}\frac{2x}{3}+3\sin \frac{2x}{3}$
Tới đây giải pt bậc 3 là xong rồi
$$\mathfrak{Curiosity}$$
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