//AN IMPLEMENTATION TO GET SUM OF G.P. SERIES....1 + 1/2 + 1/4 + 1/8 + 1/16......1/POW(2,N)////

//AN IMPLEMENTATION TO GET SUM OF G.P. SERIES....1 + 1/2 + 1/4 + 1/8 + 1/16......1/POW(2,N)////

#include<stdio.h>

#include<math.h>

int main()

{

        float sum=0,l=0,a=0,r=0;

        int n;

        printf("ENTER THE 1ST TERM:\n");

        scanf("%f",&a);

        printf("ENTER THE COMMON RATIO:\n");

        scanf("%f",&r);

        printf("ENTER THE NO OF TERMS:\n");

        scanf("%d",&n);

        sum=a*(1-(powi(r,n+1)/(1-r)));//its formula to get sum of GP series...//sum=(1-pow(r,n+1)/(1-r))//

        printf("sum=%f\n",sum);

        l=a*(1-powi(r,n-1));//last term=1-pow(r,n-1)

        printf("last term=%f\n",l);

        return 0;

}

int powi(int r,int n)//to get power of 2//

{

        float s=r;

        int i=0;

        if(n==0)

                return 1;//for n=1 pow(2,0)=1...//

        else

                for(i=1;i<=n;i++)

 r=s*r;//r is modified everytime ...s is constant 2..//

        return r;

}