# C Program to Calculate the Sum of Cos x Series

C Program to Calculate the Sum of Cos x Series

```/*
* C program to find the sum of cos(x)```
``` series
*/
#include <stdio.h>
#include <math.h>

void main()
{
int n, x1, i, j;
float x, sign, cosx, fact;

printf("Enter the number of the```
```            terms in a seriesn");
scanf("%d", &n);
printf("Enter the value of x```
```            (in degrees)n");
scanf("%f", &x);
x1 = x;
x = x * (3.142 / 180.0);
cosx = 1;
sign = -1;
for (i = 2; i <= n; i = i + 2)
{
fact = 1;
for (j = 1; j <= i; j++)
{
fact = fact * j;
}
cosx = cosx + (pow(x, i) / fact)```
```                       * sign;
sign = sign * (-1);
}
printf("Sum of the cosine series```
```            = %7.2fn", cosx);
printf("The value of cos(%d) using```
```            library function = %fn", x1,
cos(x));
}```
` `
`Output`
`Enter the number of the terms in a`
```series
3
Enter the value of x(in degrees)
90
Sum of the cosine series =   -0.23
The value of cos(90) using library```
`function = -0.000204`
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