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phantom1996
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
[TEX]\(1 + \frac{1}{{\cos x}} ){\sin ^2}x + \frac{{1 - \sqrt 2 \sin (x + \frac{\pi }{4})}}{{ {\rm{sinx}}{\rm{.}}\cos x}} = 1 + 2{ {\rm{tanx}}.c{\rm{o}}{{\rm{s}}^2}\frac{x}{2}\[/TEX]
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