CODEWITHSUNDEEP
cmathpi
user956281
user956281

Reputation: 23

Incorrect formula?

So here is a program that is supposed to calculate an approximation to the value of pi if you take enough terms into the sum which is mathematically described in the following program and calculates the expression of the root, you get a value that gets closer and closer to the value of pi the more terms you have.

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

main()
{
    int j, terms;
    double sum, precision, pi;
    printf("How many terms: "); scanf("%d", &terms);
    for(j=1;j<=terms;j++)
        sum+=1/(j*j);
    pi = sqrt(6*sum);
    printf("Pi: %lf.\n", pi);
}

But there is something making it go wrong here and I can't quite figure out what.

sum+=1/(j*j);

I thought the mistake might be in that line because all others look fine,thinking at first maybe the computer isn't counting decimals.I'm unsure.But my question is: What is it in this code that makes it malfunction?And how do I fix it?

Upvotes: 1

Views: 119

Answers (1)

Henrik
Henrik

Reputation: 23324

This performs integer division:

1/(j*j);

try this:

sum+=1.0/(j*j);

If j*j might overflow, do this 

sum+=1.0/((double)j*j);

Upvotes: 7

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