Question

Using switch statement, write 1a menu driven program for the following:

1. To find and display the sum of the series given below:
   S = x¹ − x² + x³ − x⁴ + x⁵ − ............................ − x²⁰
2. To find and display the sum of the series given below:
   S = `1/a^2 + 1/a^4 + 1/a^6 + 1/a^8 + ...................... "to n terms"`

For an incorrect option, an appropriate error message should be displayed.

Answer 1

import java.util.Scanner;

public class Q19
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("1. Sum of x^1 − x^2 + .... - x^20");
        System.out.println("2. Sum of 1/a^2 + 1/a^4 + .... to n terms");
        System.out.print("Enter your choice: ");
        int ch = in.nextInt();
        
        switch (ch) {
            case 1:
                System.out.print("Enter the value of x: ");
                int x = in.nextInt();
                long sum1 = 0;
                for (int i = 1; i <= 20; i++) {
                    int term = (int)Math.pow(x, i);
                    if (i % 2 == 0)
                        sum1 −= term;
                    else
                        sum1 += term;
                }
                System.out.println("Sum = " + sum1);
                break;

            case 2:
                System.out.print("Enter the number of terms: ");
                int n = in.nextInt();
                System.out.print("Enter the value of a: ");
                int a = in.nextInt();
                int c = 2;
                double sum2 = 0;
                for (int i = 1; i <= n; i++)  {                   
                    sum2 += (1/Math.pow(a, c));
                    c += 2;
                }                     
                System.out.println("Sum = " + sum2);
                break;

            default:
            System.out.println("Incorrect choice");
            break;
        }
    }
}