Find the principal value of the following
(i) `cos^(-1) (cos 3)` (ii) `cos^(-1) (cos 4)`
(iii) `cos^(-1) (cos 15)` (iv) `cos^(-1) (cos 30)`
(v) `cos^(-1) (cos 50)` (vi) `cos^(-1) (cos.(48pi)/(7))`

Explanation

To find the principal values of the given expressions, we will use the property that \( \cos^{-1}(\cos x) = x \) if \( x \) is in the range \( [0, \pi] \). If \( x \) is not in this range, we will adjust \( x \) by adding or subtracting multiples of \( 2\pi \) to bring it into the range.

### Step-by-step Solution:

1. **Part (i): \( \cos^{-1}(\cos 3) \)**
- Since \( 3 \) is within the range \( [0, \pi] \) (approximately \( 3.14 \)), we have:
\[
\cos^{-1}(\cos 3) = 3
...