# FreeBSD 11.0 - man page for csqrt (freebsd section 3)

```CSQRT(3)						   BSD Library Functions Manual 						  CSQRT(3)

NAME
csqrt, csqrtf, csqrtl -- complex square root functions

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#include <complex.h>

double complex
csqrt(double complex z);

float complex
csqrtf(float complex z);

long double complex
csqrtl(long double complex z);

DESCRIPTION
The csqrt(), csqrtf(), and csqrtl() functions compute the square root of z in the complex plane, with a branch cut along the negative real
axis.  In other words, csqrt(), csqrtf(), and csqrtl() always return the square root whose real part is non-negative.

RETURN VALUES
These functions return the requested square root.	The square root of 0 is +0 +- 0, where the imaginary parts of the input and respective
result have the same sign.  For infinities and NaNs, the following rules apply, with the earlier rules having precedence:

Input		Result
k + infinity*I	infinity + infinity*I	    (for all k)
-infinity + NaN*I	NaN +- infinity*I
infinity + NaN*I	infinity + NaN*I
k + NaN*I		NaN + NaN*I
NaN + k*I		NaN + NaN*I
-infinity + k*I	+0 + infinity*I
infinity + k*I	infinity + 0*I

For numbers with negative imaginary parts, the above special cases apply given the identity:
csqrt(conj(z) = conj(sqrt(z))
Note that the sign of NaN is indeterminate.  Also, if the real or imaginary part of the input is finite and an NaN is generated, an invalid
exception will be thrown.

cabs(3), fenv(3), math(3)

STANDARDS
The csqrt(), csqrtf(), and csqrtl() functions conform to ISO/IEC 9899:1999 (``ISO C99'').

BUGS
For csqrt() and csqrtl(), inexact results are not always correctly rounded.

BSD								  March 30, 2008							       BSD```