# Atn

Returns the arctangent of a number. The arctangent is the angle whose tangent is number.

See also Tan, Sin, Cos, and Pi.

### Syntax

    Atn(number)

##### number

Tangent of the angle you want.

### Usage

The range of the result is -/2 to /2 radians. To convert degrees to radians, multiply degrees by /180. To convert radians to degrees, multiply radians by 180/.

### Examples

    <!--- This snippet shows how to use Atn --->
    <HTML>
    <HEAD>
    <TITLE>
    Atn Example
    </TITLE>
    </HEAD>

    <BODY BGCOLOR=silver>
    <H3>Atn Example</H3>

    <!--- output its Atn value --->
    <CFIF IsDefined("FORM.AtnNum")>
        <CFIF IsNumeric(FORM.atnNum)>
            Atn(<CFOUTPUT>#FORM.atnNum#</CFOUTPUT>) =
              <CFOUTPUT>#Atn(FORM.atnNum)# radians =
                #Evaluate(Atn(FORM.atnNum * 180/PI())#
                  Degrees</CFOUTPUT>
        <CFELSE>
    <!--- if it is empty, output an error message --->
            <H4>Please enter a number</H4>
        </CFIF>
    </CFIF>

    <FORM ACTION="atn.cfm" METHOD="POST">
    <P>Type in a number to get its arctangent in Radians and Degrees
    <BR><INPUT TYPE="Text" NAME="atnNum" size="25">
    <P><INPUT TYPE="Submit" NAME=""> <INPUT TYPE="RESET">
    </FORM>

    </BODY>
    </HTML>