COS(3) | Library Functions Manual | COS(3)

# NAME

`cos`, `cosf`, `cosl` — cosine functions

# SYNOPSIS

Math Library (libm, -lm)
`#include <math.h>`

double
`cos`(double x);

float
`cosf`(float x);

long double
`cosl`(long double x);

# DESCRIPTION

The `cos`() function computes the cosine of x (measured in radians). The `cosf`() function is a single precision version of `cos`(). The `cosl`() function is an extended precision version of `cos`(). A large magnitude argument may yield a result with little or no significance.

# RETURN VALUES

The `cos`(), `cosf`() and `cosl`() functions return the cosine value.

# SEE ALSO

acos(3), asin(3), atan(3), atan2(3), cosh(3), sin(3), sinh(3), tan(3), tanh(3)

# STANDARDS

The `cos`() function conforms to ANSI X3.159-1989 (“ANSI C89”).

# HISTORY

A `cos`() function first appeared in Version 1 AT&T UNIX.

June 7, 2025 | Debian