how does sqrt work c++ code example

Example 1: sqrt in c++

#include <cmath>
sqrt(x);

Example 2: square root c++

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

/*
square root of a number
*/

int main(){
float num, raiz;
printf("enter a number: \t");
scanf("%f",&num);
raiz = sqrt(num);
printf("The square root of %f is: %f.\n", num, raiz);
system("pause");
return 0;    
}