compute Pi number

[herious89]

Hi Im writing a beginner program that computes the value of Pi ( pi/4 = 1 - 4/3 + 4/5 - 4/7 + 4/9 - 4/11 +... ). I've done this one, but now I want to find out how many terms do i have to use beofre i first get a value that begins with 3.14159

this is the Pi number

public class piBegins

{
    public static void main(String[]args) 
    {
  
    
    double sum = 1.0;
    for(double i = 1; i <= 200000; i++)
    sum += Math.pow(-1,i)*1.0/(2.0*i + 1.0);


        System.out.printf("Pi = %s", sum*4);
    }
}

first thing i can think of is assigning the value for sum = 3.14159

please help!

[zeroliken]

Why do it the hard way when there's already a constant for that in the math class (Math.PI) :icon_wink:

Is this H.W. where your required to make your own?

[herious89]

yes indeed it is a homework :D

[herious89]

well i think i may not need to do the reverse thing, here im trying to print all the 200,000 terms and see where the value apears to be 3.14159... but i cant :(
btw how do i set the range for i (ie. i want it to run from i=5 to i=10, when i change double i = 5, the outputs are wrong...)

public class piBegins

{
    public static void main(String[]args)  {
  
    	System.out.printf( "%s\t %s\n\n", "terms", "Pi");
    	
    double sum = 1.0;
    for(int i = 1; i <= 117000; i++)
    {
      	sum += Math.pow(-1,i)*1.0/(2.0*i + 1.0);
      	
        System.out.printf( "%s\t %.5f\n", i, sum*4);
    }
}
}

[zeroliken]

Well how about an example... here's one I found which may help you with the formula
http://www.daniweb.com/software-development/java/threads/382391/1653290#post1653290