Evaluate each of the following:
Firstly, tan = tan ……(i)
Also, coscoscos ……(ii)
From (i) and (ii),
becomes,
Now,
We know that, for any x R, represent an angle in whose tangent is x.
We know that, for any x [-1, 1], represent an angle in whose cosine is x.
Hence,
Therefore, Principal Value of is 0.