There two way to work this out.
1) Look on a ##csc## graph graph{csc x [-0.61, 17.45, -4.79, 4.24]}
According to the graph, ##csc0## is equal to undentified.
2) Trigonometric identities
According to trigonometric identities, ##cscx=1/sinx##
So, ##cscx=1/sinx## ##csc0=1/sin0## ##csc0=1/0## ##csc0## is equal to undentified.



