Question

Evaluate the following:

`tan^-1(tan  (9pi)/4)`

Answer 1

We know that

`tan^-1(tantheta)=theta,   -pi/2<theta<pi/2`

We have 

`tan^-1(tan  (9pi)/4)=tan^-1[tan(2pi+pi/4)]`

`=tan^-1[tan(pi/4)]`

`=pi/4`