If `veca and vecb` are two vectors of magnitude 1 inclined at `120^(@)`, then find the angle between `vecb and vecb-veca`.

Explanation

To find the angle between the vectors \(\vec{b}\) and \(\vec{b} - \vec{a}\), we can follow these steps:

### Step 1: Understand the given information
We know that both vectors \(\vec{a}\) and \(\vec{b}\) are unit vectors (magnitude = 1) and that the angle between them is \(120^\circ\).

### Step 2: Calculate the dot product \(\vec{a} \cdot \vec{b}\)
Using the formula for the dot product:
\[
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