## Friday, 13 May 2016

### Chapter 2 Exercise 17, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

*2.17 (Science: wind-chill temperature) How cold is it outside? The temperature alone is not enough to provide the answer. Other factors including wind speed, relative humidity, and sunshine play important roles in determining coldness outside. In 2001, the National Weather Service (NWS) implemented the new wind-chill temperature to measure the coldness using temperature and wind speed. The formula is $twc=35.74+0.6215\cdot ta-35.75\cdot {v}^{0.16}+0.4275ta\cdot {v}^{0.16}$ where ta is the outside temperature measured in degrees Fahrenheit and v is the speed measured in miles per hour. twc is the wind-chill temperature. The formula cannot be used for wind speeds below 2 mph or temperatures below -58 ºF or above 41ºF. Write a program that prompts the user to enter a temperature between -58 ºF and 41ºF and a wind speed greater than or equal to 2 and displays the wind-chill temperature. Use Math.pow(a, b) to compute ${v}^{0.16}$. Here is a sample run:

Enter the temperature in Fahrenheit between -58°F and 41°F:5.3
Enter the wind speed (>=2) in miles per hour: 6
The wind chill index is -5.56707

import java.util.Scanner;

public class ProgrammingEx2_17 {

public static void main(String[] args) {
Scanner input = new Scanner(System.in);

System.out
.print("Enter the temperature in Fahrenheit between -58?F and 41?F:");
double ta = input.nextDouble();
System.out.print("Enter the wind speed (>=2) in miles per hour:");
double v = input.nextDouble();
double twc = 35.74 + 0.6215 * ta - 35.75 * Math.pow(v, 0.16) + 0.4275
* ta * Math.pow(v, 0.16);

System.out.print("The wind chill index is " + twc);

}
}

### Chapter 2 Exercise 16, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

2.16 (Geometry: area of a hexagon) Write a program that prompts the user to enter the
side of a hexagon and displays its area. The formula for computing the area of a
hexagon is

where s is the length of a side. Here is a sample run:

Enter the side: 5.5
The area of the hexagon is 78.5895

import java.util.Scanner;

public class ProgrammingEx2_16 {

public static void main(String[] args) {
Scanner input = new Scanner(System.in);

System.out.print("Enter the side:");
double s = input.nextDouble();
double area = (3 * Math.sqrt(3) / 2) * Math.pow(s, 2);
System.out.print("The area of the hexagon is " + area);

}

}

### Chapter 2 Exercise 15, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

2.15 (Geometry: distance of two points) Write a program that prompts the user to enter two points (x1, y1) and (x2, y2) and displays their distance between them. The formula for computing the distance is  Note that you can use Math.pow(a, 0.5) to compute 2a. Here is a sample run:
Enter x1 and y1: 1.5 -3.4
Enter x2 and y2: 4 5
The distance between the two points is 8.764131445842194

import java.util.Scanner;

public class ProgrammingEx2_15 {

public static void main(String[] args) {

Scanner input = new Scanner(System.in);

System.out.print("Enter x1 and y1:");
double x1 = input.nextDouble();
double y1 = input.nextDouble();
System.out.print("Enter x2 and y2:");
double x2 = input.nextDouble();
double y2 = input.nextDouble();
double distance = Math.sqrt(Math.pow((x2 - x1), 2)
+ Math.pow((y2 - y1), 2));
System.out.print("The distance between the two points is  " + distance);

}
}