# C++ Exercises: Find the sum of the series [ x - x^3 + x^5 + ......]

## C++ Exercises: For Loop Exercise-25 with Solution

Write a program in C++ to find the sum of the series [ x - x^3 + x^5 + ......].

**Sample Solution**:-

**C++ Code :**

```
#include <iostream> // Including input-output stream header
#include <math.h> // Including math library for pow function
using namespace std; // Using standard namespace to avoid writing std::
int main() // Start of the main function
{
float x, sum, ctr; // Declaration of float variables 'x' (input value), 'sum' (to store the sum), 'ctr' (for intermediate calculation)
int i, n, m, mm, nn = 0; // Declaration of integer variables 'i' (loop counter), 'n' (number of terms), 'm', 'mm', 'nn' (intermediate values)
cout << "\n\n Display the sum of the series [ x - x^3 + x^5 + ......]\n"; // Displaying a message on the console
cout << "------------------------------------------------------------\n";
cout << " Input the value of x: "; // Prompting the user to input the value of x
cin >> x; // Reading the input value as 'x'
cout << " Input number of terms: "; // Prompting the user to input the number of terms
cin >> n; // Reading the input value as the number of terms
sum = x; // Initializing 'sum' with the first term (x)
m = -1; // Initializing 'm' as -1 to alternate the signs of terms in the series
cout << "The values of series:" << endl; // Displaying a message
cout << sum << endl; // Displaying the first term of the series (x)
for (i = 1; i < n; i++) // Loop to calculate 'n' terms of the series
{
ctr = (2 * i + 1); // Calculating the power for each term of the series (x^ctr)
mm = pow(x, ctr); // Calculating x raised to the power 'ctr'
nn = mm * m; // Calculating the term (x^ctr) with alternate signs
cout << nn << endl; // Displaying the calculated term of the series
sum = sum + nn; // Adding the term to the sum
m = m * (-1); // Changing the sign for the next term
}
cout << "\n The sum of the series upto " << n << " term is: " << sum << endl; // Displaying the sum of the series
}
```

Sample Output:

Display the sum of the series [ x - x^3 + x^5 + ......] ------------------------------------------------------------ Input the value of x: 2 Input number of terms: 5 The values of series: 2 -8 32 -128 512 The sum of the series upto 5 term is: 410

**Flowchart: **

**C++ Code Editor:**

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https://www.w3resource.com/cpp-exercises/for-loop/cpp-for-loop-exercise-25.php

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