Find the principal value of each of the following :
[ Formula: cos (2π + x) = cos x , cos is positive in the first quadrant. ]
= 
[Formula: cos-1(cos x) = x]
= 
1
Find the principal value of each of the following :
[ Formula: cos (2π + x) = cos x , cos is positive in the first quadrant. ]
= [Formula: cos-1(cos x) = x]
=