The sqrt function in C computes the nonnegative square root of x (sqrt parameters). A domain error occurs if the argument is less than zero. It is declared in math.h and takes one argument in the form of double and returns the value of type double.

Syntax of sqrt function in C:

You can also use the sqrtf() function to work specifically with float and sqrtl() to work with long double type. See the below syntax.

float       sqrtf( float arg ); (1)	(since C99)

double      sqrt( double arg ); (2)

long double sqrtl( long double arg );(3) (since C99)

Parameters:

x => floating types (double)

Return value:

If no errors occur, sqrt functions return √x.

C program to understand the working of sqrt function:

Consider the below code where I am passing different characters in the sqrt function. You can see the output of this function with entered input.

#include <math.h>
#include <stdio.h>

int main()
{
    double data, squareRoot;

    printf("Enter a number: ");
    scanf("%lf", &data);

    // Compute square root of data
    squareRoot = sqrt(data);

    //print square root of data
    printf("Square root of %f =  %f",data, squareRoot);

    return 0;
}

Output:

Enter a number: 16
Square root of 16.000000 = 4.000000

Note: A domain error occurs if and only if an input argument is outside the domain over which the mathematical function is defined. On a domain error, the function returns an implementation-defined value.

Error handling

Errors are reported as specified in math_errhandling. A 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.

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

#pragma STDC FENV_ACCESS ON

int main(void)
{
    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");
    }

    return 0;
}

Output:

sqrt(-1.0) = nan
errno == EDOM: Domain error
FE_INVALID was raised

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