Note that x ≠( 2n + 1) π / 2 is not part of domain since for these values of x, tan x is undefined.
Similarly domain & range of cosec, sec & cot can be defined. o
Since cosec x = 1 / sin x, the domain of y = cosec x is the set { x: x ∈ R and x ≠ n π, n ∈ Z } and range is the set { y: y ∈ R, y ≥ 1 or y ≤ – 1 }. o
The domain of y = sec x is the set { x: x ∈ R and x ≠( 2n + 1) π / 2, n ∈ Z } and range is the set { y: y ∈ R, y ≤ – 1or y ≥ 1 }.