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.Dd April 1, 2017
.Dt TANPI 3
.Os
.Sh NAME
.Nm tanpi ,
.Nm tanpif ,
.Nm tanpil
.Nd half\(encycle tangent functions
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn tanpi "double x"
.Ft float
.Fn tanpif "float x"
.Ft long double
.Fn tanpil "long double x"
.Sh DESCRIPTION
The
.Fn tanpi ,
.Fn tanpif ,
and
.Fn tanpil
functions compute the tangent of
.Fa "\(*p \(mu x"
and measure angles in half-cycles.
.Sh RETURN VALUES
The
.Fn tanpi ,
.Fn tanpif ,
and
.Fn tanpil
functions returns
.Fn tan "\(*p \(mu x" .
If \*(Bax\*(Ba \*(Ge 2^(p - 1)
where p is the floating\(enpoint precision of
.Ar x ,
then the returned value is \*(Pm0 and it has no significance.
.Sh SPECIAL VALUES
.Bl -tag
.It
.Fn tanpi \*(Pm0
returns \*(Pm0.
.It
.Fn tanpi \*(Pmn
returns \*(Pm0 for positive integers
.Ar n .
.It
.Fn tanpi \*(Pmn/2
returns \*(Na for n > 0 and raises an FE_INVALID exception.
.It
.Fn tanpi \*(Pm\(if
return an \*(Na and raises an FE_INVALID exception.
.It
.Fn tanpi \*(Na
return an \*(Na and raises an FE_INVALID exception.
.El
.Sh SEE ALSO
.Xr cos 3 ,
.Xr cospi 3 ,
.Xr fenv 3 ,
.Xr math 3 ,
.Xr sin 3 ,
.Xr sinpi 3 ,
.Xr tan 3
.Sh AUTHORS
The half\(encycle trignometric functions were written by
.An Steven G. Kargl Aq Mt kargl@FreeBSD.org .
.Sh STANDARDS
These functions conform to
IEEE Std 754\(tm\(en2008 ,
\(dqIEEE Standard for Floating-Point Arithmetic\(dq
and to
ISO/IEC TS 18661-4 ,
\(dqInformation technology \(em Programming languages, their environments,
and system software interfaces \(em Floating\(enpoint extensions for
C\(dq \(em Part 4: Supplementary functions.