# NAME

sqrt - calculate the square root of a number

sqrt, sqrtf, sqrtl - square root function

# LIBRARY

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

# SYNOPSIS

``#include <math.h>``

## Prototype

``````double sqrt(double x);
``````
``````#include <math.h>
double sqrt(double x);
float sqrtf(float x);
long double sqrtl(long double x);``````

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

sqrtf(), sqrtl():

``````    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE``````

# DESCRIPTION

This function calculates the square root of `x`.

These functions return the nonnegative square root of `x`.

# RETURN VALUE

This function returns, as a `double`, the square root of `x`.

On success, these functions return the square root of `x`.

If `x` is a NaN, a NaN is returned.

If `x` is +0 (-0), +0 (-0) is returned.

If `x` is positive infinity, positive infinity is returned.

If `x` is less than -0, a domain error occurs, and a NaN is returned.

# EXAMPLE

``````#include <math.h>#include <stdio.h>
int main(void)
{
printf("This is CS%i\n", (int) sqrt(2500));
}
``````

# ERRORS

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: `x` less than -0

`errno` is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.

# ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

 Interface Attribute Value sqrt(), sqrtf(), sqrtl() Thread safety MT-Safe

# STANDARDS

C11, POSIX.1-2008.

# HISTORY

C99, POSIX.1-2001.

The variant returning `double` also conforms to SVr4, 4.3BSD, C89.