[tex]VT= \frac{sinx}{1+cosx}+\frac{cosx}{sinx}=\frac{sin^{2}x+cos^{2}x+cosx}{(cosx+1)sinx}=\frac{1+cosx}{sinx(1+cosx)}=\frac{1}{sinx}= VT[/tex] auto qua màn nhé )
[tex]sin^{2}\alpha =\frac{16}{25}\Rightarrow cos^{2}\alpha =1-sin^{2}\alpha =\frac{9}{25}[/tex] vì [tex]\frac{\Pi }{2}< \alpha < \Pi[/tex] nên cos <0 suy ra [tex]cos\alpha =\frac{-3}{5}; tan\alpha =\frac{sin\alpha }{cos\alpha }=\frac{-4}{3} ; cot\alpha =\frac{1}{tan\alpha }=\frac{-3}{4}[/tex] auto qua màn nhé bạn )