If `hatn` is a unit vector in the direction of the vector `vecA`, them :

Options

A. `hatn=(vecA)/(|vecA|)`
B. `hatn = (|vecA|)/(vecA)`
C. `hatn = |vecA|vecA`
D. `hatn = vecA`

Explanation

To solve the problem, we need to understand the definition of a unit vector and how it relates to the vector \(\vec{A}\).

### Step-by-Step Solution:

1. **Understanding Unit Vectors**:
A unit vector is defined as a vector that has a magnitude of 1. It is often represented by a hat notation, such as \(\hat{n}\).

2. **Definition of \(\hat{n}\)**:
Given that \(\hat{n}\) is a unit vector in the direction of the vector \(\vec{A}\), we can express \(\hat{n}\) mathematically. The unit vector in the direction of any vector \(\vec{A}\) is given by:
\[ \hat{n} = \frac{\vec{A}}{|\vec{A}|} \]
where \(|\vec{A}|\) is the magnitude of the vector \(\vec{A}\).

3. **Magnitude of \(\vec{A}\)**:
The magnitude of a vector \(\vec{A}\) can be calculated using the formula:
\[ |\vec{A}| = \sqrt{A_x^2 + A_y^2 + A_z^2} \]
where \(A_x\), \(A_y\), and \(A_z\) are the components of the vector \(\vec{A}\).

4. **Conclusion**:
Since \(\hat{n}\) is defined as \(\frac{\vec{A}}{|\vec{A}|}\), we can conclude that the first option given in the question is indeed correct.

### Final Answer:
The correct expression for the unit vector \(\hat{n}\) in the direction of the vector \(\vec{A}\) is:
\[ \hat{n} = \frac{\vec{A}}{|\vec{A}|} \]