# ATAN2 function

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.

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

Note   Do not select the row or column headers.

Selecting an example from Help
• Press CTRL+C.
• In the worksheet, select cell A1, and press CTRL+V.
• 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.
A B
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)

Applies to:
Excel 2007