If ` vec A =vec B- vec C`, then determine the angle betwee `vec A and vec B`.

Explanation

To determine the angle between the vectors \( \vec{A} \) and \( \vec{B} \) given that \( \vec{A} = \vec{B} - \vec{C} \), we can follow these steps:

### Step-by-Step Solution:

1. **Express \( \vec{C} \) in terms of \( \vec{A} \) and \( \vec{B} \)**:
\[ \vec{C} = \vec{B} - \vec{A} \]
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