﻿ ATAN2 function

ATAN2 function

This article describes the formula syntax and usage of the ATAN2function in Microsoft Excel.

Description

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)

The ATAN2 function syntax has the following arguments:

• X_num    Required. The x-coordinate of the point.

• Y_num    Required. 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 do I copy an example?

1. Select the example in this article.

Important   Do not select the row or column headers.

Selecting an example from Help

2. Press CTRL+C.

3. In Excel, create a blank workbook or worksheet.

4. In the worksheet, select cell A1, and press CTRL+V.

Important   For the example to work properly, you must paste it into cell A1 of the worksheet.

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.

After you copy the example to a blank worksheet, you can adapt it to suit your needs.

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 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 2010, Excel Starter, Excel Online, SharePoint Online

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