Find the principal value of: `cos^(-1)(-1/2)`

Explanation

To find the principal value of \( \cos^{-1}(-\frac{1}{2}) \), we can follow these steps:

### Step 1: Set up the equation
Let \( y = \cos^{-1}(-\frac{1}{2}) \). This implies that:
\[ \cos y = -\frac{1}{2} \]

...