c 程序计算 e^x 的值，最多修正 10 位小数

Question

I am writing a program that calculates the value of e^x, according to the expansion formula.I need to print the answer so that it is correct upto 10 decimal places. I have tried to do it using, for, while and do while loop, however I cannot figure out where to terminate the loop, which condition to use to terminate the loop. i have written the code as follows:

#include<stdio.h>
#include<math.h>
int factorial(int x);
int main()
{
    int x,n;
    float sum,d_1;
    printf("Enter the value of power :");
    scanf("%d",&x);
    n=1;sum=1;
    while(sum <= %.10f)
    {
        d_1=pow(x,n)/factorial(n);
        sum=sum+d_1;
        n++;
    }
    printf("Answer is %f",sum);
    return 0;
}
int factorial(int y)
{
    int fact=1,i;
    for(i=1;i<=y;i++)
    {
        fact=fact*i;
    }
    return(fact);
}

and i am getting the error message expected expression before %. Please help.

Answer 1

You want to terminate the loop when the current term is smaller than some value. Also you want the loop to execute at least once, so a do-while loop is preferable:

n = -1;
do {
    n++;
    d_1 = pow(x, n) / factorial(n);
    sum = sum + d_1;
} while (d_1 > epsilon);

As mentioned in the comments, there are other issues with the code when it comes to precision and overflow but that is a different story.