Why does program output x1 = Nan, x2 = Nan? - c

Question

I can't work out why my program isn't doing what it's supposed to do. The task was to make a c program that can solve quadratic using two c files. This is the code called interface.c that we got to work with, nothing has to be changed on this one:
#include <stdio.h>
void abc (void);
int a, b, c;
extern double x1real, x1imag, x2real, x2imag;
static void get_parameters (void)
{
scanf("%d", &a);
scanf("%d", &b);
scanf("%d", &c);
}
void print_solution(void)
{
printf("The roots of %dx^2 + %dx + %d are:\n",a,b,c);
if(x1imag == 0 && x2imag == 0)
{
if(x1real == x2real)
{
printf("x = %.4f\n", x1real);
}
else
{
printf("x1 = %.4f, x2 = %.4f\n", x1real, x2real);
}
}
else
{
printf("x1 = %.4f+%.4fi, x2 = %.4f-%.4fi\n", x1real, x1imag, x2real, x2imag);
}
}
int main (void)
{
int runs, run;
scanf("%d",&runs);
for(run=0; run < runs; run++)
{
get_parameters();
abc();
print_solution();
}
return 0;
}
Next is the code I made which isn't working, there seems to go something wrong with the integer types I think. With every quadratic formula it will output x1 = nan x2 = nan. There is something wrong with the integer type but can't figure out which.
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
extern int a, b, c;
double x1real, x1imag, x2real, x2imag;
int discriminant(void)
{
int discriminant;
discriminant = (pow(b,2)-4*a*c);
return discriminant;
}
void abc (void)
{
if (discriminant() > 0)
{
x1real = (-b - sqrt(discriminant()))/(2*a);
x2real = (-b + sqrt(discriminant()))/(2*a);
x1imag = 0;
x2imag = 0;
}
else
{
x1real = x2real = (-b) / (2*a);
x1imag = (-b - sqrt(-discriminant())) / (2*a);
x2imag = (-b + sqrt(-discriminant())) / (2*a);
}
return;
}
input:
4
2 0 0
1 3 2
3 4 9
1 0 1
output:
The roots of 2x^2 + 0x + 0 are:
x = 0.0000
The roots of 1x^2 + 3x + 2 are:
x1 = -1.0000, x2 = -2.0000
The roots of 3x^2 + 4x + 9 are:
x1 = -0.6667+-2.2653i, x2 = -0.6667-0.9319i
The roots of 1x^2 + 0x + 1 are:
x1 = 0.0000+-1.0000i, x2 = 0.0000-1.0000i
suspected output:
The roots of 2x^2 + 0x + 0 are:
x = 0.0000
The roots of 1x^2 + 3x + 2 are:
x1 = -1.0000, x2 = -2.0000
The roots of 3x^2 + 4x + 9 are:
x1 = -0.6667+1.5986i, x2 = -0.6667-1.5986i
The roots of 1x^2 + 0x + 1 are:
x1 = 0.0000+1.0000i, x2 = 0.0000-1.0000i

Answer 1

Quadratic formula?
conditional expression of「b^2-4ac≧0」 is not called, is it?
int discriminant(void)
{
int discriminant;
discriminant = (pow(b,2)-4*a*c);
return discriminant;
}
void abc (void)
{
// if (discriminant > 0) // it doesn't call [int discriminant(void)]
if (discriminant() >= 0)
{
x1real = (-b - sqrt(discriminant()))/(2*a);
x2real = (-b + sqrt(discriminant()))/(2*a);
x1imag = 0;
x2imag = 0;
}
else
{
x1real = x2real = (-b) / (2*a);
x1imag = (-b - sqrt(-discriminant())) / (2*a);
x2imag = (-b + sqrt(-discriminant())) / (2*a);
}
return;
}
(An addition)
static void get_parameters (void)
{
do {
scanf("%d", &a);
scanf("%d", &b);
scanf("%d", &c);
} while(a == 0)
}