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+.\" Copyright (c) 2007-2008 David Schultz <das@FreeBSD.org>
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd March 30, 2008
+.Dt CSQRT 3
+.Os
+.Sh NAME
+.Nm csqrt ,
+.Nm csqrtf ,
+.Nm csqrtl
+.Nd complex square root functions
+.Sh LIBRARY
+.Lb libm
+.Sh SYNOPSIS
+.In complex.h
+.Ft double complex
+.Fn csqrt "double complex z"
+.Ft float complex
+.Fn csqrtf "float complex z"
+.Ft long double complex
+.Fn csqrtl "long double complex z"
+.Sh DESCRIPTION
+The
+.Fn csqrt ,
+.Fn csqrtf ,
+and
+.Fn csqrtl
+functions compute the square root of
+.Fa z
+in the complex plane, with a branch cut along the negative real axis.
+In other words,
+.Fn csqrt ,
+.Fn csqrtf ,
+and
+.Fn csqrtl
+always return the square root whose real part is non-negative.
+.Sh RETURN VALUES
+These functions return the requested square root.
+The square root of 0 is
+.Li +0 \*(Pm 0 ,
+where the imaginary parts of the input and respective result have
+the same sign.
+For infinities and \*(Nas, the following rules apply, with the
+earlier rules having precedence:
+.Bl -column -offset indent "-\*(If + \*(Na*I" "\*(If \*(Pm \*(If*I  " "(for all k)"
+.Em Input	Result
+k + \*(If*I	\*(If + \*(If*I	(for all k)
+-\*(If + \*(Na*I	\*(Na \*(Pm \*(If*I
+\*(If + \*(Na*I	\*(If + \*(Na*I
+k + \*(Na*I	\*(Na + \*(Na*I
+\*(Na + k*I	\*(Na + \*(Na*I
+-\*(If + k*I	+0 + \*(If*I
+\*(If + k*I	\*(If + 0*I
+.El
+.Pp
+For numbers with negative imaginary parts, the above special cases
+apply given the identity:
+.Dl csqrt(conj(z) = conj(sqrt(z))
+Note that the sign of \*(Na is indeterminate.
+Also, if the real or imaginary part of the input is finite and
+an \*(Na is generated, an invalid exception will be thrown.
+.Sh SEE ALSO
+.Xr cabs 3 ,
+.Xr fenv 3 ,
+.Xr math 3 ,
+.Sh STANDARDS
+The
+.Fn csqrt ,
+.Fn csqrtf ,
+and
+.Fn csqrtl
+functions conform to
+.St -isoC-99 .
+.Sh BUGS
+For
+.Fn csqrt
+and
+.Fn csqrtl ,
+inexact results are not always correctly rounded.