**The Program in C# Program to Find Sum of series[ x-x^3+x^5-x^7+x^9-..] is given below:**

```
using System;
namespace SumOfSeries
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello Codeauri Family, enter the value of X here:");
double x = double.Parse(Console.ReadLine());
Console.WriteLine("Similarly, enter the number of terms in the series:");
int n = int.Parse(Console.ReadLine());
double sum = 0;
int sign = 1;
for (int i = 0; i < n; i++)
{
double factorial = 1;
for (int j = 1; j <= 2 * i + 1; j++)
{
factorial *= j;
}
sum += sign * Math.Pow(x, 2 * i + 1) / factorial;
sign = -sign;
}
Console.WriteLine("Okay, the sum of the series is: " + sum);
Console.ReadLine();
}
}
}
```

## Output:

Hello Codeauri Family, enter the value of X here:

8

Similarly, enter the number of terms in the series:

4

Okay, the sum of the series is: -220.368253968254

## Pro-Tips💡

Here are the step by step execution of above program:

- Read the value of X and the number of terms in the series from the user.
- Initialize a variable ‘sum’ to store the sum of the series, and a variable ‘sign’ to keep track of the sign of each term in the series.
- Start a loop from 0 to (n-1), where n is the number of terms in the series.
- In the loop, calculate the factorial of (2 * i + 1) for each term.
- Calculate the sum of each term by adding the value of (sign * x^(2 * i + 1) / factorial) to the ‘sum’ variable.
- Reverse the sign of each term by assigning the opposite value to the ‘sign’ variable.
- After the loop, print the final sum of the series.

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