Find PI recursively using the formula:

PI calculation formula

The exercise asks for 1000 multiples. Here we ask the user to enter how many multiples he wants.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
#include <stdio.h>
#include <math.h>
double f(int n){
    if(n==1)
        return sqrt(2);
    else
        return sqrt(2+f(n-1));
}

double product(int n){
    if(n==1)
        return 2;
    else
        return 2/f(n-1)*product(n-1);
}

int main(){
    double prod=1;
    int i,multiples;
   
    printf("How many multiples: ");
    scanf("%d",&multiples);
   
    printf("pi= %.15lf",product(multiples));
   
    return 0;
}