S
snowangel1103
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
a) [TEX]1+cos2x+cos3x = 2cosx.cos2x[/TEX]
b[TEX]\frac{cos^2x}{sinx+cos(7pi+x)}=2(1+sinx)[/TEX]
b[TEX]\frac{cos^2x}{sinx+cos(7pi+x)}=2(1+sinx)[/TEX]
Last edited by a moderator: