**Implementation Notes:**

- $H$ is generally expressed in degrees, not radians. Math libraries generally return inverse tangents in radians, not degrees. In Excel, use the DEGREES function to convert radians to degrees.
- In computing $H$, be careful with the inverse tangent since $u$ could be zero. Instead, use special
math functions to do this. In the Standard C library and most other math libraries, this function is called
**atan2**and is used calling atan2(v, u). In Microsoft Excel, it is called**ATAN2**and its use is ATAN2(u, v).**Note the argument reversal!**These special functions will compute the proper inverse tangents without needing to worry about "divide by zero" conditions. Additionally, atan2 will also handle the quadrants for you.