Answer: Cosecant is undefined at 180°.
Explanation:
Since we have given that
Cosecant i.e. cosec Θ
Since we know from the "trigonometric table"
If Θ = 45°

so, cosecant is defined.
If Θ = 60°,

So, cosecant is defined again.
If Θ = 180°

So, it is not defined.
If Θ = 270°
then

so, it is defined.
Hence, cosecant is undefined at 180°.