How can I find sine value with using sine series

Quote:

i want to find sin of x using sine series . x-x^3/3!+......
i want to find this using pow function

Then do it, start working.

We do not do your HomeWork.
HomeWork is not set to test your skills at begging other people to do your work, it is set to make you think and to help your teacher to check your understanding of the courses you have taken and also the problems you have at applying them.
Any failure of you will help your teacher spot your weaknesses and set remedial actions.
So, give it a try, reread your lessons and start working. If you are stuck on a specific problem, show your code and explain this exact problem, we might help.

As programmer, your job is to create algorithms that solve specific problems and you can't rely on someone else to eternally do it for you, so there is a time where you will have to learn how to. And the sooner, the better.
When you just ask for the solution, it is like trying to learn to drive a car by having someone else training.
Creating an algorithm is basically finding the maths and make necessary adaptation to fit your actual problem.

There are several errors. For instance

Quote:

for(i=1;i<=n;i+2)

is wrong, the last statement in the for clause ha no effect, it should be i+=2. Moreover, the fact variable must be initialized immediately before the factorial loop (by the way, it is better using a float variable for holding the factorial result, because it becomes large soon).
You might fix your code this way:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
  int i,j,n,ch,p;
  float fact;
  float x,sum,angle;
  do
  {
    printf("\n1. Sine series\n2. Cosine series\n3. Exponential series\n4. Exit\nEnter your choice: ");
    scanf("%d",&ch);
    switch(ch)
    {
    case 1:
      printf("\nEnter the value of x(in degree)and n in sine series.\n");
      scanf("%f",&x);
      scanf("%d",&n);
      angle = x;
      x=x*M_PI/180;
      sum=0.0;
      p=0;
      for(i=1;i<=n;i+=2)
      {
        fact=1;
        for(j=2;j<=i;j++)
        {
          fact=fact*j;
        }
        sum+=(pow(-1,p)*((float)pow(x,i)/fact));
        p++;
      }
      printf("\nsin(%.2f)=%.2f\n",angle,sum);
    break;
    //...

However I would factor out the sin computation in a function, and I would also compute the terms incrementally, e.g.

#include <stdio.h>
#include <math.h>

double comp_sin( double x, int n)
{
  double sign = 1.0;
  double fact = 1.0;
  double sum=0.0;
  double x2 = x * x;

  int k;

  for (k=0; k<n; ++k)
  {
    sum += (sign * x) / fact;
    // update the factors
    sign = sign > 0.0 ? -1.0 : 1.0; // toggle the sign
    fact *= (2.0 * k + 2.0) * (2.0 * k + 3.0); // compute the next 'factorial' factor
    x *= x2; // compute the next 'power' factor
  }
  return sum;
}


int main()
{
  int n;
  double angle;

  printf("please enter the angle in degres and the number of terms of the series\n");
  scanf("%lf", &angle);
  scanf("%d", &n);

  printf("sin(%g) = %g\n", angle, comp_sin(angle*M_PI/180, n ));

  return 0;
}