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.rm #[ #] #H #V #F C
.IX Title "atan Cg"
.TH atan Cg "" "Cg Toolkit 1.5" "Cg Standard Library"
.UC
.SH "NAME"
\&\fBatan\fR \- returns arctangent of scalars and vectors.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 5
\&  float  atan( float  a );
\&  float1 atan( float2 a );
\&  float2 atan( float2 a );
\&  float3 atan( float3 a );
\&  float4 atan( float4 a );
.Ve
.Vb 5
\&  half   atan( half  a );
\&  half1  atan( half2 a );
\&  half2  atan( half2 a );
\&  half3  atan( half3 a );
\&  half4  atan( half4 a );
.Ve
.Vb 5
\&  fixed  atan( fixed  a );
\&  fixed1 atan( fixed2 a );
\&  fixed2 atan( fixed2 a );
\&  fixed3 atan( fixed3 a );
\&  fixed4 atan( fixed4 a );
.Ve
.SH "PARAMETERS"
.IX Header "PARAMETERS"
.Ip "a" 8
.IX Item "a"
Vector or scalar of which to determine the arctangent.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Returns the arctangent of x in the range of \-pi/2 to pi/2 radians.
.PP
For vectors, the returned vector contains the arctangent of each
element of the input vector.
.SH "REFERENCE IMPLEMENTATION"
.IX Header "REFERENCE IMPLEMENTATION"
\&\fBatan\fR for a \fBfloat\fR scalar could be implemented like this.
.PP
.Vb 3
\&  float atan(float x) {
\&      return atan2(x, float(1));
\&  }
.Ve
atan2 is typically implemented as an approximation.
.SH "PROFILE SUPPORT"
.IX Header "PROFILE SUPPORT"
\&\fBatan\fR is supported in all profiles except fp20.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
the abs manpage,
the acos manpage,
the asin manpage,
the atan2 manpage.
the sqrt manpage,
the tan manpage
