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

## C For Loop: Exercise-24 with Solution

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

This C program calculates the sum of the series x - x^3 + x^5 - ... up to a specified number of terms. The user inputs the value of x and the number of terms n. The program then uses a loop to compute each term of the series, alternating the sign and increasing the exponent by 2 for each subsequent term. Finally, the program sums the terms and prints the result.

**Sample Solution:**

**C Code:**

```
#include <stdio.h> // Include the standard input/output header file.
#include <math.h> // Include the math functions header file.
void main()
{
int x, sum, ctr; // Declare variables to store input and intermediate results.
int i, n, m, mm, nn; // Declare loop control variables and intermediate results.
printf("Input the value of x :"); // Prompt the user for input.
scanf("%d", &x); // Read the value of 'x' from the user.
printf("Input number of terms : "); // Prompt the user for input.
scanf("%d", &n); // Read the value of 'n' from the user.
sum = x; // Initialize 'sum' to 'x' as the first term in the series.
m = -1; // Initialize 'm' to -1.
printf("The values of the series: \n"); // Print a message.
printf("%d\n", x); // Print the first term of the series.
for (i = 1; i < n; i++) // Loop to calculate subsequent terms in the series.
{
ctr = (2 * i + 1); // Calculate the power of 'x' using the given formula.
mm = pow(x, ctr); // Calculate the value of 'x' raised to the power 'ctr'.
nn = mm * m; // Multiply 'mm' with 'm'.
printf("%d \n", nn); // Print the calculated term.
sum = sum + nn; // Add the term to the running sum.
m = m * (-1); // Toggle the value of 'm' between -1 and 1.
}
printf("\nThe sum = %d\n", sum); // Print the final sum.
}
```

Output:

Input the value of x :2 Input number of terms : 5 The values of the series: 2 -8 32 -128 512 The sum = 410

**Flowchart: **

**C Programming Code Editor:**

**Previous:** Write a program in C to display the sum of the series [ 1+x+x^2/2!+x^3/3!+....].

**Next:** Write a program in C to display the n terms of square natural number and their sum.

**What is the difficulty level of this exercise?**

Test your Programming skills with w3resource's quiz.

**Weekly Trends and Language Statistics**- Weekly Trends and Language Statistics