Question

Evaluate the following:

`cot^-1{cot  ((21pi)/4)}`

Answer 1

We know that

cot^-1 (cot θ) = θ,   (0, π)

We have

`cot^-1{cot  (21pi)/4}=cot^-1[cot(5pi+pi/4)]`

`=cot^-1(cot  pi/4)`

`=pi/4`