ATAN2

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 worksheet.

How to copy an example

1. Create a blank workbook or worksheet.
2. Select the example in the Help topic.

   Note Do not select the row or column headers.

   Selecting an example from Help

3. Press CTRL+C.
4. In the worksheet, select cell A1, and press CTRL+V.
5. To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

See also:

• ATAN
• ATANH
• Math and trigonometry functions
• PI
• TAN