Discuss t lie singularities of 1cos1zSolutionIn mathematics

Discuss t lie singularities of 1/cos(1/z).

In mathematics, a singularity is in general a point at which a given mathematical object is not defined, or a point of an exceptional set where it fails to be well-behaved in some particular way, such as differentiability.

that neither of the limits lim z0 1/cos(1/z) and lim z0cos(1/z) exist. Therefore the singularity is of essential type.