## nomarhere

i need help with a homework problem, it's writing a program that approximates the sum of

1 + x/1! + (x^2)/2! + (x^3)/3! + ... + (x^n)/n!

we're supposed to write a program that takes a value x as input and outputs this sum for n taken to be each of the values of 1 to 100. and we're supposed to have the ouput be in a 1o X 10 form, so like 10 values on 10 lines.

i know we are supposed to use a nested loop. a for loop in a a do while loop, but i just can't figure out how to write the code for the summation, i can do it mathematically on paper, but it just doesn't make sense to me in writing it in source code. please if you could help me i would greatly appreciate it.

-M

## grumpier 149

For information on the help you can expect here with homework problems, have a look here.

If you have a further look through the forums, there was a thread on your exact topic (more precisely, a discussion of how to evaluate that particular summation) a week or so back. However, you need to do some work for yourself, so I'll leave finding that thread as as something for you to do.

## nomarhere

this is what i have:

``````#include <iostream>
#include <cmath>
using namespace std;

int main ()
{
double x, n, Real_result, Partial =	1, fact = 1;
char ans;

cout << "Input a value of 'X' for which you would like to calculate e^x\n";
cin >> x;

Real_result = exp (x);

cout << "The Actual value of e^x is: " << Real_result << endl << endl;

cout << "Would you like to approximate that same value? \n";
cin >> ans;

if (ans = 'y' || 'Y')
{

do
{
for (n = 1; n <= 100; n++)
{
Partial = Partial + pow(x, n)/fact;
n++;
fact++;
cout << Partial << endl;
}

} while ( n <= 100 );

}

return 0 ;
}``````

and i know there is a problem with my for loop, i'm jsut not sure what.

as for finding the the other 'exact' topic. i found it, some time ago and it did me no good which is why i made my own post.

-M

## grumpier 149

as for finding the the other 'exact' topic. i found it, some time ago and it did me no good which is why i made my own post.

Well, you get nothing further from me. That thread contains all the information you need. It doesn't give a canned answer though: you need to put in a little effort rather than relying on spoon-feeding.