C
connguoivietnam


câu 1
[TEX]cos^4x + sin^4( x + \frac{\pi}{4}) = sin2xcos2x - \frac{5}{4}tan(x + \frac{\pi}{4})tan(x - \frac{\pi}{4})[/TEX]
[TEX]cos^4x + sin^4( x + \frac{\pi}{4}) = sin2xcos2x - \frac{5}{4}tan(x + \frac{\pi}{4})tan(x - \frac{\pi}{4})[/TEX]
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