This article describes the formula syntax and usage of the ATAN2 function in Microsoft Excel.
Description
Returns the arctangent, or inverse tangent, of the specified x and ycoordinates. The arctangent is the angle from the xaxis to a line containing the origin (0, 0) and a point with coordinates (x_num, y_num). The angle is given in radians between pi and pi, excluding pi.
Syntax
ATAN2(x_num, y_num)
The ATAN2 function syntax has the following arguments:

X_num Required. The xcoordinate of the point.

Y_num Required. The ycoordinate of the point.
Remarks

A positive result represents a counterclockwise angle from the xaxis; a negative result represents a clockwise angle.

ATAN2(a,b) equals ATAN(b/a), except that a can equal 0 in ATAN2.

If both x_num and y_num are 0, ATAN2 returns the #DIV/0! error value.

To express the arctangent in degrees, multiply the result by 180/PI( ) or use the DEGREES function.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.