练习2-15 求简单交错序列前N项和 (15 分)

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <math.h>
 4 
 5 
 6 /* run this program using the console pauser or add your own getch, system("pause") or input loop */
 7 
 8 int main(int argc, char *argv[]) {
 9 int x;
10 double sum=0,n;
11 scanf("%d",&x);
12 for(n=1;n<=3*x-2;n+=3)
13 sum+=pow((-1),n+1)*(1.0/n);
14 
15 printf("sum = %.3f\n",sum);
16 return 0;
17 }