代碼塊不打印特定格式

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; 
} 

然而，我的輸出是

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 

我只是一個初學者，是格式錯誤？ 使用代碼塊，在C.

寫

Answer 1

試試這個：

#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; 
} 

記住：負荷數學庫這樣的 - > gcc的 「文件名」 -lm