import cs1.Keyboard;
public class Pi2 {
   private static double termValue(int term) { 
      return 4.0/(2.0 * term - 1.0); 
   }
   public static double pi(int term, double sum, double epsilon) {
      double tn = termValue(term); if (term % 2 == 0) tn = -tn; // even terms are negative
      System.out.println("term=" + term + "\t" + "value=" + tn + "\t" + "sum=" + sum);
      if (Math.abs(tn) < epsilon) return sum + tn; 
      else return pi(term + 1, sum + tn, epsilon);
   }
   public static void main(String[] args) {
      System.out.println("This program estimates PI using an infinite series.");
      System.out.println("Enter minimum term size, e.g. 0.001");
      double epsilon = Keyboard.readDouble();
      System.out.println("Pi is " + pi(1, 0.0, epsilon));
   }
}