Hello I need to create this summation and if you put the number 30000 the response should the number of pi, however it's not working here's the summation and here's the code.

#include <stdio.h>  
#include <stdlib.h> 
#include <string.h> 
#include <time.h>   
#include <limits.h> 
#include <ctype.h>  
#include <stdbool.h>

int main( void ){

int num, k;
double pi= 0;

printf("Digite o total de termos >=30000: ");
scanf("%d", &num);
if (num < 30000){
    printf("Erro.");
    
}else {
    for (k = 1; k<= num; k  ){
        if (k % 2 == 0){
            pi = (double)(-1)/ (2*k -1);
            
            
        }else{
            pi =  (double)(1)/ (2*k -1);
        
           
        }
        pi = pi * 4;
    }
   
    printf("O valor de pi e %f", pi);
    
    
}



return 0; }

CodePudding user response：

Here is a general way to sum things up:

double sum(int from, int to, double (*f)(int)) {
    double ret = 0.0;

    for(int i=from; i<to; i  )
        ret =f(i);

    return ret;
}

And then you can write this function:

double fun(int current) {
    double sign = current %2 == 0 ? -1.0 : 1.0;
    return sign / (2*current - 1)
}

Finally, call it like this:

double pi = sum(1, num, fun);

Do note that this is probably not a good way to go if you're a beginner student that is looking for a solution to some homework.

CodePudding user response：

#include <stdio.h>

int main(void) {
    double pi=0;
    
    for(int k=1; k<=3000;   k)
    {
        pi  = (2.*(k%2)-1) / (2*k-1);   // This line does a summation, and uses floating point math (Not Integer Math)
    }
    
    printf("Pi : %f\n", 4*pi);
    return 0;
}