The angle between the two vectors `vecA=hati+2hatj-hatk` and `vecB=-hati+hatj-2hatk`

Explanation

To find the angle between the two vectors \(\vec{A} = \hat{i} + 2\hat{j} - \hat{k}\) and \(\vec{B} = -\hat{i} + \hat{j} - 2\hat{k}\), we can use the formula for the cosine of the angle between two vectors:

\[ \cos \theta = \frac{\vec{A} \cdot \vec{B}}{|\vec{A}| |\vec{B}|} \]

### Step 1: Calculate the dot product \(\vec{A} \cdot \vec{B}\)

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