What is ATAN2 used for?
How is ATAN2 calculated?
What is the difference between atan and ATAN2 in Excel?
For points in the second and third quadrants of the coordinate system, the ATAN function will return the angle relative to the negative x-axis direction. The ATAN2 function, by comparison, returns the angle relative to the positive x-axis which is the standard for measuring angles.