Btukfyl

Hope your ok
I'll be happy if you help me out with this problem ... Thnx

I wrote this Code for the Formula : "http://up.upinja.com/zvhev.png"

Console.WriteLine("Enter two Numbers to start the Equation (X=Number , N=Power)" + "");

int X = int.Parse(Console.ReadLine());

int N = int.Parse(Console.ReadLine());

double sum = 0;

double up = 1;

int down = 1;



double sentence;

for (int i = 1; i < N; i++)

{

up = Math.Pow(X, N);

down = N * i;

sentence = up / down;

sum += sentence;

}

Console.WriteLine("The Sum is : " + sum);

I want that math Formula to be done in C# way....
my Code is running but wrong answer I get ...
Could you plz help me to fix it ?

n! represents Factorial. Please refer Factorial to read about Factorial.

A sample factorial function in C# is as follows:

long Factorial(long value)

{          

    if (value == 0)

        return 1;



    return value * Factorial(value - 1);

}

Also, following line needs correction.

up = Math.Pow(X, N);

The exponent part needs to increase according to your formula. It needs to be

up = Math.Pow(X, i);

Use this:

Console.WriteLine("Enter two Numbers to start the Equation (X=Number , N=Power)" + "");

int X = int.Parse(Console.ReadLine());

int N = int.Parse(Console.ReadLine());

double sum = 0;

double up = 1;

int down = 1;



double sentence;

for (int i = 1; i <= N; i++)

//Change < to <=

{

    up = Math.Pow(X, i);

    //This is a for loop i created to get the factorial of any number, sometimes creating your own functions may be worth it

    for (int a = N, a > 0, a--)

    {

     //Function of this Loop : multiply the value of the denominator by its value - 1 to get the factorial of  the number

        down *= a;

    } 

    sentence = up / down;

    sum += sentence;

}

Console.WriteLine("The Sum is : " + sum);

You can actually simplify this quite a bit. But first, what's wrong with your existing code is that you're not computing i! correctly. The sequence you're actually computing right now is:

X^N / N + X^N / (2 * N) + X^N / (3 * N) + ... + X^N / ((N - 1) * N)

A few things:
- The loop has an off-by-one issue
- The numerator is raised to the wrong power
- The denominator of these needs to be i!

Factorials are defined through a simple recurrence relation:

i! = i * (i - 1)! and 0! = 1

Or, in other words, the product of the first i consecutive natural numbers. So one way to correct this is by creating a method called Factorial:

static long Factorial(int i) 

{ 

    long product = 1;

    while (i > 0) {

        product *= i;

        --i;

    }

    return product;

}

Then you can fix your loop this way:

for (int i = 1; i < N; i++)

{

    sum += Math.Pow(X, i) / Factorial(i);

}

However, we're redoing a lot of work every iteration of the loop that we don't need to do. This is where the simplification comes in. The general formula for the i'th term is this:

C[i] = X^i / i!

But we can also write this in terms of the term that came before it:

C[i] = C[i-1] * X / i

So we can rewrite the loop like this:

double lastTerm = 1;

for (int i = 1; i <= N; ++i)

{

    // Cast to double here or, probably better, make X a double in the first place.

    lastTerm *= (double) X / i;

    sum += lastTerm;

}

This has several advantages:

• It'll generally be faster since we're doing less work each iteration (Math.Pow computes arbitrary powers, so it's a bit slower than just multiplying).


• It'll be less prone to numerical issues. Factorials get really big really fast. In fact, 21! is already too big to store in a long so if your N is bigger than that, everything will break.

Something wrong in pow, shoud incremental value

    up = Math.Pow(X, i);