代码块不打印特定格式

Question

#include <stdio.h>
#include <math.h>
int main(void)
{
 double a, b, c, root1, root2;
 printf("Input the coefficient a => ");
 scanf("%lf", &a);
 printf("Input the coefficient b => ");
 scanf("%lf", &b);
 printf("Input the coefficient c => ");
 scanf("%lf", &c);
/* Compute the roots. */
root1 = (- b + sqrt(b*b-4*a*c))/(2*a);
root2 = (- b - sqrt(b*b-4*a*c))/(2*a);
printf("The first root is %8.3f\n", root1);
printf("The second root is %8.3f\n", root2);
return 0;
}

但是，我的输出是

Input the coefficient a => 232
Input the coefficient b => 23
Input the coefficient c => 2
The first root is      nan
The second root is      nan 

我只是个初学者，是不是格式有误？使用代码块，用C编写。

Answer 1

试试这个：

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

int main(void)
{
 double a, b, c, root1, root2;
 double temp;
 printf("Input the coefficient a => ");
 scanf("%lf", &a);
 printf("Input the coefficient b => ");
 scanf("%lf", &b);
 printf("Input the coefficient c => ");
 scanf("%lf", &c);
/* Compute the roots. */
temp = b*b-4*a*c;
if (temp >= 0) {
    root1 = (- b + sqrt(temp))/(2*a);
    root2 = (- b - sqrt(temp))/(2*a);
    printf("The first root is %8.3f\n", root1);
    printf("The second root is %8.3f\n", root2);  
} else {
    printf("There is no root!\n");
}

return 0;
}

记住:加载数学库，就像这样：->

-> "fileName“-lm