---
name: "ccos"
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/ccos"
---

# ccos(3)

complex cosine function

## NAME

ccos, ccosf, ccosl - complex cosine function

## LIBRARY

Math library (*libm*, *-lm*)

## SYNOPSIS

```
#include <complex.h>
```

**double complex ccos(double complex** *z***);** **float complex ccosf(float complex** *z***);** **long double complex ccosl(long double complex** *z***);**

## DESCRIPTION

These functions calculate the complex cosine of *z*.

The complex cosine function is defined as:

```
ccos(z) = (exp(i * z) + exp(-i * z)) / 2
```

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **ccos**(), **ccosf**(), **ccosl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

glibc 2.1. C99, POSIX.1-2001.

## SEE ALSO

[**cabs**(3)](/cabs/3.md), [**cacos**(3)](/cacos/3.md), [**csin**(3)](/csin/3.md), [**ctan**(3)](/ctan/3.md), [**complex**(7)](/complex/7.md)