/C

# sqrt, sqrtf, sqrtl

Defined in header `<math.h>`
`float       sqrtf( float arg );`
(1) (since C99)
`double      sqrt( double arg );`
(2)
`long double sqrtl( long double arg );`
(3) (since C99)
Defined in header `<tgmath.h>`
`#define sqrt( arg )`
(4) (since C99)
1-3) Computes square root of `arg`.
4) Type-generic macro: If `arg` has type `long double`, `sqrtl` is called. Otherwise, if `arg` has integer type or the type `double`, `sqrt` is called. Otherwise, `sqrtf` is called. If `arg` is complex or imaginary, then the macro invokes the corresponding complex function (`csqrtf`, `csqrt`, `csqrtl`).

### Parameters

 arg - floating point value

### Return value

If no errors occur, square root of `arg` (arg), is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a range error occurs due to underflow, the correct result (after rounding) is returned.

### Error handling

Errors are reported as specified in math_errhandling.

Domain error occurs if `arg` is less than zero.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If the argument is less than -0, `FE_INVALID` is raised and NaN is returned.
• If the argument is +∞ or ±0, it is returned, unmodified.
• If the argument is NaN, NaN is returned

`sqrt` is required by the IEEE standard to be exact. The only other operations required to be exact are the arithmetic operators and the function `fma`. After rounding to the return type (using default rounding mode), the result of `sqrt` is indistinguishable from the infinitely precise result. In other words, the error is less than 0.5 ulp. Other functions, including `pow`, are not so constrained.

### Example

```#include <stdio.h>
#include <math.h>
#include <errno.h>
#include <fenv.h>

#pragma STDC FENV_ACCESS ON

int main(void)
{
// normal use
printf("sqrt(100) = %f\n", sqrt(100));
printf("sqrt(2) = %f\n", sqrt(2));
printf("golden ratio = %f\n", (1+sqrt(5))/2);
// special values
printf("sqrt(-0) = %f\n", sqrt(-0.0));
// error handling
errno = 0; feclearexcept(FE_ALL_EXCEPT);
printf("sqrt(-1.0) = %f\n", sqrt(-1));
if(errno == EDOM) perror("    errno == EDOM");
if(fetestexcept(FE_INVALID)) puts("    FE_INVALID was raised");
}```

Possible output:

```sqrt(100) = 10.000000
sqrt(2) = 1.414214
golden ratio = 1.618034
sqrt(-0) = -0.000000
sqrt(-1.0) = -nan
errno = EDOM: Numerical argument out of domain
FE_INVALID was raised```
• C11 standard (ISO/IEC 9899:2011):
• 7.12.7.5 The sqrt functions (p: 249)
• 7.25 Type-generic math <tgmath.h> (p: 373-375)
• F.10.4.5 The sqrt functions (p: 525)
• C99 standard (ISO/IEC 9899:1999):
• 7.12.7.5 The sqrt functions (p: 229-230)
• 7.22 Type-generic math <tgmath.h> (p: 335-337)
• F.9.4.5 The sqrt functions (p: 462)
• C89/C90 standard (ISO/IEC 9899:1990):
• 4.5.5.2 The sqrt function
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