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bear12a1


@};-Ai biet thi lam giup minh nha
1<x.[TEX]cos^2[/TEX] x<([TEX]\pi[/TEX]+2)/4 ( x[TEX]\in[/TEX] [0; [TEX]\pi[/TEX]/ 4])
1<x.[TEX]cos^2[/TEX] x<([TEX]\pi[/TEX]+2)/4 ( x[TEX]\in[/TEX] [0; [TEX]\pi[/TEX]/ 4])
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