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	Các bình luận về: Đề bài: Cho  $\begin{cases}x,y,z,t \in (-\frac{\pi}{2};\frac{\pi}{2}) \\\sin x+\sin y+\sin z+\sin t= 1\\\cos 2x+\cos 2y+\cos 2z+\cos 2t \geq \frac{10}{3}\end{cases}$Chứng minh rằng:  $ x,y,z,t \in [0;\frac{\pi}{6}]$	</title>
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