If 0 ≤ θ <2π​, for what​ angles, θ​, if​ any, is tan θ ​undefined?

Question

 If 0 ≤ θ <2π, for what angles, θ, if any, is tan θ undefined?

Answer 1

tan=sin/cos

look on the unit circle

when the cos is 0, tan is undefined

tan is undefined for 90º and for 270º