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

char input[100];
float answer;

int main()
{
        printf("Enter value to find square root:\n> ");
        fgets(input,sizeof(input),stdin);
        sscanf(input,"%f",&answer);
        
        float sqrtf(float answer);

        printf("Calculated answer: %f\n", answer);
             
        return 0;
}

bash-3.1$ gcc -g -Wall -o 6-1 6-1.c
bash-3.1$ 6-1                      
Enter value to find square root:
> 11
Calculated answer: 11.000000
bash-3.1$