A cylinder of radius $R$ and mass $m$ is wound to a string and suspended from a vertical wall (figure). The cylinder does not slide on the wall. The coefficient of friction between the wall and the cylinder is $\mu$. Select the correct statement(s) 

The cylinder has a tendency to rotate anticlockwise , this will be prevented by upward frictional force acting on the cylinder .

Therefore , $T \cos \alpha +f=mg$  ………………(1)

$T\sin \alpha =N$             …………………………….(2)

$TR=fR$                 

$T=f\le \mu N$       ……………………………………(3)

$\frac{N}{\sin \alpha }\le \mu N$

$\mu \ge \cos ec \alpha$

$T \cos \alpha +T=mg$

$T=\frac{mg}{1+\cos \alpha }<mg$