#include <math.h>
int main()
{
double x,num,sum=0
int i=1,j,flag=1
double jie
scanf("%lf",&x)
while(1)
{
j=i
jie=1.0
while(j)
{//计算阶乘
jie*=j--
}
num=pow(x,i++)/jie//pow为计算x的i次方
if(fabs(num)<0.00001)//fabs计算绝对值
{
break
}
if(flag)//是加是减用flag标志
{
sum+=num
flag=0
}
else
{
sum-=num
flag=1
}
//printf("sum=%lf,num=%lf,jie=%ld,i=%d\n",sum,num,jie,i)
}
printf("sum=%.2f",sum)
getch()
return 0
}
#include <stdio.h>int main()
{double s=0,t
int i,n
scanf("%d",&n)
for(i=1i<=ni++)
{t=i*i
if(i%2)s+=1-1/t
else s-=1-1/t
}
printf("%.3lf\n",s)
return 0
}
#include <stdio.h>main()
{
float sum
int i, j=1, k=2
for(i = 1i <= 20i++) {
printf("%d %d\n", j, k)
sum = 1.0 * j / k
k += j
j = k - j
}
printf("前20项数列和是: %f\n", sum)
}
