Thread: help w/ PI Math java program

im currently in entry level java class and need help with a code..here are my instructions

Mathematicians define the constant PI to be
PI = 4 *( 1 - 1/(2*2-1) + 1/(2*2+1) - 1/(2*4-1) + 1/(2*4+1) - 1/(2*6-1) + 1/(2*6+1)- . . . .format . . . . . - 1/(2*i-1) + 1/(2*i+1) )
Note that i starts at 2 and is incremented by 2. The higher the i, the more precise PI will be. Also note that the higher the value of i, the smaller the value of PI.

Write a program that displays the value of PI for i = 100, 200, 300, . . ,1000. Output should be something like this :
when i is 100 PI is xxxx
when i is 200 PI is xxxx
etc . .
when i is 900 PI is xxxx
when i is 1000 PI is xxxx

Once you have this working, enhance the program, add another section. The next section of the program should determine the value of i needed to achieve a value of PI that is equal to or slightly smaller than 3.1419. The program should output the following message :
value of i to give PI equal or smaller than 3.1419 is xxxxxx


and here is my code so far, i underlined the part where im getting an errors
should i put each value of PI in an if statement?? im kinda stuck right now thanks

public class ConstantPI {
public static void main(String[] args)
{
 
 
[U]int i = 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000;[/U]
double pi4 = 1.0;
for(int j = 2; j <= i; j += 2)
pi4 = pi4 - 1/(2*(double)j - 1) + 1/(2*(double)j + 1);
double pi = 4.0*pi4;
System.out.println("When i is " + i + " PI is " + pi);
}
 
}

btw crossposted thanks

help w/ PI Math java program - Java Forums

Hmmmmmm....I think I mighta found the problem.

You had some extra brackets that you didn't need.

public class Assign3_Roberts {
public static void main(String[] args)
{
for (int i = 100; i <= 1000; i += 100) {
    double pi4 = 1.0;
    for(int j = 2; j <= i; j += 2)
    pi4 = pi4 - 1/(2*(double)j - 1) + 1/(2*(double)j + 1);
    double pi = 4.0*pi4;
    System.out.println("When i is " + i + " PI is " + pi);
 
    }
 
//next section
//determine value of i
 
int i = 0;
double pi = 100;
 
do
{
i ++;
double pi4 = 1.0;
for(int j = 2; j <= i; j += 2)
pi4 = pi4 - 1/(2*(double)j - 1) + 1/(2*(double)j + 1);
pi = 4.0*pi4;
} while (pi > 3.1419);
System.out.println("value of i to give PI equal or smaller than 3.1419 is " + i);
}
}

 

 ----jGRASP: operation complete.



 ----jGRASP exec: java Assign3_Roberts



When i is 100 PI is 3.1514934010709914

When i is 200 PI is 3.1465677471829556

When i is 300 PI is 3.1449149035588526

When i is 400 PI is 3.144086415298761

When i is 500 PI is 3.143588659585789

When i is 600 PI is 3.143256545948974

When i is 700 PI is 3.1430191863875865

When i is 800 PI is 3.142841092554028

When i is 900 PI is 3.1427025311614294

When i is 1000 PI is 3.1425916543395442

value of i to give PI equal or smaller than 3.1419 is 3254

I'm still baffled as to how that lower for loop even works since it appears that i is less than j from the beginning.



Oh well. It is valid. I checked it.