Show that the area of the triangle contained between the `vec a and vecb` is is one half of the magnitude of `veca xx vecb`.

Explanation

To show that the area of the triangle formed by vectors **a** and **b** is half of the magnitude of the cross product of **a** and **b**, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Vectors**:
Let vectors **a** and **b** originate from the same point. The triangle formed by these vectors has its vertices at the origin, the tip of vector **a**, and the tip of vector **b**.

2. **Area of the Triangle**:
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