Thus, cos–1 is a function whose domain is [–1, 1] and range
could be any of the intervals [–π, 0], [0, π], [π, 2π] etc Corresponding to each such interval, we get a branch of the
function cos–1 The branch with range [0, π] is called the principal
value branch of the function cos–1 We write
cos–1 : [–1, 1] → [0, π]