Cho $\displaystyle x_{1},x_{2},.......,x_{10}\in \left[0,\frac{\pi}{2}\right]$ thoả mãn $\sin^2x_{1}+\sin^2x_{2}+.......+\sin^2x_{10} = 1$
Tìm min:$\displaystyle T= \frac{\cos x_{1}+\cos x_{2}+......+\cos x_{10}}{\sin x_{1}+\sin x_{2}+.....+\sin x_{10}}$
