WorksheetFunction.Atan2 Method (Excel)
Returns the arctangent, or inverse tangent, of the specified x- and y-coordinates. The arctangent is the angle from the x-axis 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.
A positive result represents a counterclockwise angle from the x-axis; 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 an error value.
To express the arctangent in degrees, multiply the result by 180/PI( ) or use the Degrees method.