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

Explanation

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

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

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