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.

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

    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.

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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



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