第1个回答 2018-05-02
#include <stdio.h>
int main(int argc, char *argv[]){
int n, x = 3;
double = 0.0;
double sum = 0.0, a = 0, b = 1;
scanf("%d",&n);
for(int i = 0; i <n; i++){
if( i == 0 )
sum = sum;
else {
a += x;
b += x;
if( i % 2 == 1 )
sum += ((-a) / b);
else
sum += (a / b);
x += 2;
}
}
printf("%lf\n",sum);
return 0;
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