运行之后总是0.49972989，想问问各位朋友是哪里出问题了？

Question

大一，对着它看一天了，真看不出来哪出了问题，不敢问同学，希望各位帮帮忙，谢谢了！

Answer 1

你可以参考这个，两种写法。 https://ask.csdn.net/questions/7798480/53927579?spm=1001.2014.3001.5504

#include<stdio.h>
int main()
{
  int i, n, one;
  double x, s, a, b, x2;
  scanf("%lf %n", &x, &n);
  x2 = x * x;
  s = x;
  a = x;
  b = 1;
  one = 1;
  for (i = 2; i <= n; i++)
  {
    one *= -1;
    a *= x2;
    b *= (2 * i - 1) * (2 * i - 2);
    s += one * a / b;
  }
  printf("%.10lf", s);
}