源代码

#include <stdio.h>

int main()

{

int num = 1, sign = 1, term = 1;

double sum = 1.00;

while (num <= 20)

{

sign = -sign;

term = term + 2;

sum += ( (double) sign / term);

num++;

}

printf("前20项和=%0.3f", sum);

}

运行结果图