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I'm trying to calculate e^x, without any built-in functions such as Math.exp. This is what I have so far:

Code:

public static double math_ex(int iter, int x) {
double ex = 0;
int i = 1;
while(i <= iter) {
if (i == 1) {
ex += x;
} else {
ex += Math.pow(x,(double)i/factorial(i));
}
i++;
}
ex += 1;
return ex;
}

My input is:

Code:

Enter iterations:
6
Enter x:
3
e^3 = 11.989024

But when I use the calculator to figure it out, it is 20.0855........

Can you see anything thats wrong with my function?

Not a java programmer, but if Math.exp is a built=in function, I assume that Math.pow is as well.

Don't know what is wrong with your code, but is simple multiplying in a loop not easier.

something like

Code:

result=1;
while(iter--)
result *= x;
return result;

This is not bug free.

[edit]
OK, it's still vague but the factorial is probably to calculate e; so calculate e first and fill it in in place of x. Will be a bit faster as well as you only have to calculate e once.[/edit]

Last edited by Wim Sturkenboom; 07-24-2007 at 07:20 AM.

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