---
name: "csqrt"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/csqrt"
---

# csqrt(3)

complex square root

## NAME

csqrt, csqrtf, csqrtl - complex square root

## 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

These functions calculate the complex square root of *z*, with a branch cut along the negative real axis. (That means that *csqrt(-1+eps\*I)* will be close to I while *csqrt(-1-eps\*I)* will be close to -I, *if eps* is a small positive real number.)

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **csqrt**(), **csqrtf**(), **csqrtl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

glibc 2.1. C99, POSIX.1-2001.

## SEE ALSO

[**cabs**(3)](/cabs/3.md), [**cexp**(3)](/cexp/3.md), [**complex**(7)](/complex/7.md)