calculate pi
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Thread: calculate pi

  1. #1
    Join Date
    Mar 2013
    Posts
    5

    calculate pi

    hi everyone I feel so stupid asking help for these.
    i NEED HELP with these part of my code my prompt said :
    (computing Π (PI) ) You can approximate (PI) value by using the following
    series:
    Π = 4( 1 – 1/3 + 1/5 – 1/7 + 1/9 – 1/11 + … - 1/(2i -1) + 1/(2i + 1)
    Write a method that calculate value of π by using the above series, using
    the following header:
    public static double pi()
    assume i = 1000000

    ok so I have been testing it but I really did get any far :

    for ( double i = 1; i< 1000000; i+=2) {

    // with these I try to increment the value of i to get to the serie.


    //I did these after and test it and the output is all wrong and I know it


    sum = (1/((2*i)+1));

    sum = sum + (1/((2*i)-1));

    sum ++;

    double pi = 4*(sum);


    // I know is wrong I but I can´t figure it out what to do.


    I am a first semester student of computer science I got the beging of the semester really fast but these is getting harder and my professor is not helping that much..

    if someone can help me pleaseee!

  2. #2
    Join Date
    Dec 2012
    Location
    England
    Posts
    2,335

    Re: calculate pi

    Possibly its the maths that you need some help with. The general term in the series you are using is 1/(2 * n - 1) where n starts at 1 and continues in increments of 1 until its terminating value - in your case 1000000. So when n = 1, the term is 1/(2 * 1 - 1) which is 1/1, n = 2 the term is 1/(2 * 2 - 1) which is 1/3 etc. Every even term is negative so when n is even the term is subtracted from the sum rather than added. The result is then four times the sum.

    How a go with this info and post back your code if you still have problems. Please use [code] tags when posting code to make it readable (click go advanced, highlight the code and then click '#'). As it's homwork I can't really give you the code but I'll comment on anything you post back.

  3. #3
    Join Date
    Mar 2013
    Posts
    5

    Re: calculate pi

    thankss

    so I got these so far,
    but I don´t know how to get the total value of the sum, and also if I should update the variable sum ?

    Code:
     public class Pi{
    	 public static void main(String[] args)
          {
     
    	sum =0;
    	
    	 for (int i=3 ; i< 1000000; i+=2){
    	 
    	if (sum%2==0){
    	
    	sum = 1/(2 * i - 1);
    	 }
    	else {
    	    
    	sum =  1/(2 * i + 1);
    
    	 }
    	
    	}

  4. #4
    Join Date
    Dec 2012
    Location
    England
    Posts
    2,335

    Re: calculate pi

    That's not c++. That looks like java or c#? This is the c++ forum.

  5. #5
    Join Date
    Mar 2013
    Posts
    5

    Re: calculate pi

    I know but I couldn´t find out a C# forum can u still give me feedback?

  6. #6
    Join Date
    Dec 2012
    Location
    England
    Posts
    2,335

    Re: calculate pi

    On the main forum page the c# forum is called c-sharp programming under the header .net programming. You need to scroll down the page until you find it. I really suggest you re-post there for c# related questions.

    However, the help I can give is this. You loop needs to start at 1 until 1000000 and go up in increments of 1. For every value of the loop you need to calculate the individual term using 1 / (2 * i - 1). Then once you have calculated the term, add it to the sum if i is odd or subtract it from the sum if i is even.

  7. #7
    Join Date
    Mar 2013
    Posts
    5

    Re: calculate pi

    thankss! I appreciate the help

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