atan.3

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th ATAN III 4/30/73
.sh NAME
atan, atan2 \*- arc tangent function
.sh SYNOPSIS
.ft B
jsr    pc,atan\fR[\fB2\fR]\fB
.s3
.br
double atan(x)
.br
double x;
.br
.s3
double atan2(x, y)
.br
double x, y;
.ft R
.sh DESCRIPTION
The
\fIatan\fR entry returns the arc tangent
of fr0 in fr0;
from C, the arc tangent of \fIx\fR is returned.
The range is \*-\*p/2 to \*p/2.
The \fIatan2\fR entry returns the arc tangent
of fr0/fr1 in fr0;
from C, the arc tangent of
\fIx/y\fR is returned.
The range is \*-\*p to \(*p.
.sh DIAGNOSTIC
There is no error return.
.sh BUGS