binroot.txt

利用二分法求一个方程的实数近似根。

/*利用二分法求方程 f()x=x*x*x-x-1  的一个近似实根*/

#include <stdio.h>
double count_function(x)  /*该函数用来计算方程的根*/
double x;
{double y;
 y=x*x*x-x-1;
 return y;
}
main()
{double a1,b1,ab,little_error=1e-4;   /*little_error 为误差指标*/
 a1=1;
 b1=2;
 printf("   a1                b1\n\n\n"); /*用以记录a1和b1的各种可能的取值*/
 while ((b1-a1)>little_error)
    {ab=(a1+b1)/2;
     printf("   %1f          %1f\n",a1,b1);
     if (count_function(ab)==0)
     printf("the root of the equation is %1f\n",ab);
     else
       if (count_function(a1)*count_function(ab)<0) /*高等数学中的“零点推论”*/
       {
        b1=ab;
       }
     else
       if (count_function(b1)*count_function(ab)<0)
       {
        a1=ab;
       }
     }
 printf("\n\nthe root of the equation is    %1f\n",ab); /*输出方程的根*/
 getch();
}