Thus
cot –1 can be defined as a function whose domain is the R and range as any of the
Rationalised 2023-24
INVERSE TRIGONOMETRIC FUNCTIONS     25
intervals (–π, 0), (0, π), (π, 2π) etc These intervals give different branches of the
function cot –1 The function with range (0, π) is called the principal value branch of
the function cot –1 We thus have
cot–1 : R → (0, π)
The graphs of y = cot x and y = cot–1x are given in Fig 2