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 }.