ATAN2

See Also

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.

Syntax

ATAN2(x_num,y_num)

X_num is the x-coordinate of the point.

Y_num is the y-coordinate of the point.

Remarks

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 the #DIV/0! error value.
To express the arctangent in degrees, multiply the result by 180/PI( ) or use the DEGREES function.

Example

The example may be easier to understand if you copy it to a blank spreadsheet.

How?

Create a blank spreadsheet.
Select the example in the Help topic.

Selecting an example from Help
Press CTRL+C.
In the spreadsheet, select cell A1, and press CTRL+V.
To switch between viewing the formula that returns the result and the result in the cell, select the cell and press F2 and then ENTER, or click Commands and Options on the spreadsheet toolbar, click the Formula tab, and look in the Formula in active cell (active cell) box.

Formula	Description (Result)
=ATAN2(1, 1)	Arctangent of the point 1,1 in radians, pi/4 (0.785398)
=ATAN2(-1, -1)	Arctangent of the point -1,-1 in radians, -3*pi/4 (-2.35619)
=ATAN2(-1, -1)*180/PI()	Arctangent of the point 1,1 in degrees (-135)
=DEGREES(ATAN2(-1, -1))	Arctangent of the point 1,1 in degrees (-135)