import cs1.Keyboard;
public class Pi3 {
   private static double termValue(int term) { 
      return 4.0/(2.0 * term - 1.0); 
   }
   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();
      int term = 1; double sum = 0.0; double tn;
      do
      {
         tn = termValue(term); if (term % 2 == 0) tn = -tn; // even terms are negative
         sum += tn;
//         System.out.println("term=" + term + "\t" + "value=" + tn + "\t" + "PI=" + sum);
         term++;
      } while (Math.abs(tn) > epsilon);
      System.out.println("PI=" + sum);
   }
}