, is bijective and its range
is R – {–1, 1} Thus sec–1 can be defined as a function whose domain is R– (–1, 1) and
range could be any of the intervals [– π, 0] – { 2
−π }, [0, π] – { 2
π }, [π, 2π] – { 3
2
π } etc Corresponding to each of these intervals, we get different branches of the function sec–1 The branch with range [0, π] – { 2
π } is called the principal value branch of the
function sec–1