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System.out.printf(“The area of the pentagon is %.2f”,a);

}

}

4.2

====================java语言程序设计基础篇课后============================================

import java.util.Scanner;

public class disizhang {

public static void main(String[] args){

Scanner input = new Scanner(System.in);

System.out.print("Enter point 1 (latitude and longitude) in degrees: ");

double x1 = input.nextDouble();

double y1 = input.nextDouble();

System.out.print("Enter point 2 (latitude and longitude) in degrees: ");

double x2 = input.nextDouble();

double y2 = input.nextDouble();

double d = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));

System.out.println(“The distance between the two points is “+d+” km”);

}

}

4.3

================================================================

public class disizhang {

public static void main(String[] args){

double x1 = 35.;

double y1 = -80.;

double x2 = 32.0;

double y2 = -81.0;

double dcs = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));

x2 = 33.;

y2 = -84.;

double dca = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));

x1 = 28.;

y1 = -81.;

double doa = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));

x2 = 32.0;

y2 = -81.0;

double dos = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));

x1 = 33.;

y1 = -84.0;

double das = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));

double s1 = (dca+dcs+das)/2;

double s2 = (doa+dos+das)/2;

double a = Math.sqrt(s1*(s1-dca)(s1-dcs)(s1-das))+Math.sqrt(s2*(s2-doa)(s2-dos)(s2-das));

System.out.println(“The area is “+a+” km^2”);

}

}

4.4

================================================================

import java.util.Scanner;

public class disizhang {

public static void main(String[] args){

final double PI = 3.;

Scanner input = new Scanner(System.in);

System.out.print("Enter the side: ");

double s = input.nextDouble();

double a = 6ss/(4*Math.tan(PI/6));

System.out.println("The area of the hexagon is "+a);

}

}

4.5

================================================================

import java.util.Scanner;

public class disizhang {

public static void main(String[] args){

final double PI = 3.;

Scanner input = new Scanner(System.in);

System.out.print("Enter the number of sides: ");

int n = input.nextInt();

System.out.print("Enter the side: ");

double s = input.nextDouble();

double a = nss/(4*Math.tan(PI/n));

System.out.println("The area of the polygon is "+a);

}

}

4.6

================================================================

public class disizhang {

public static void main(String[] args){

final double PI = 3.;

double alpha1 = Math.random()2PI;

double alpha2 = Math.random()2PI;

double alpha3 = Math.random()2PI;

double x1 = 40*Math.cos(alpha1);

double y1 = 40*Math.sin(alpha1);

double x2 = 40*Math.cos(alpha2);

double y2 = 40*Math.sin(alpha2);

double x3 = 40*Math.cos(alpha3);

double y3 = 40*Math.sin(alpha3);

double a = Math.sqrt((x1-x2)(x1-x2)+(y1-y2)(y1-y2));

double b = Math.sqrt((x2-x3)(x2-x3)+(y2-y3)(y2-y3));

double c = Math.sqrt((x1-x3)(x1-x3)+(y1-y3)(y1-y3));

double aa = Math.toDegrees(Math.acos((aa-bb-cc)/(-2b*c)));

double ab = Math.toDegrees(Math.acos((bb-aa-cc)/(-2a*c)));

double ac = Math.toDegrees(Math.acos((cc-bb-aa)/(-2a*b)));

System.out.println("The three angles are: “+aa+” “+ab+” "+ac);

}

}

4.7

================================================================

import java.util.Scanner;

public class disizhang {

public static void main(String[] args){

final double PI = 3.;

Scanner input = new Scanner(System.in);

System.out.print("Enter the radius of the bounding circle: ");

double r = input.nextDouble();

double base = 0.1*PI;

System.out.println(“The coordinates of fibe points on the pentagon are”);

for(int i=0;i<5;i++)

{

System.out.printf(“(%.2f, %.2f)%n”,rMath.cos(base),rMath.sin(base));

base+=0.4*PI;

}

}

}

4.8

================================================================

import java.util.Scanner;

public class disizhang {

public static void main(String[] args){

Scanner input = new Scanner(System.in);

System.out.print("Ent6er an ASCII code: ");

int num = input.nextInt();

char str = (char)num;

System.out.printf(“The character for ASCII code %d is %c”,num,str);

}

}

4.9

================================================================

import java.util.Scanner;

public class disizhang {

public static void main(String[] args){

Scanner input = new Scanner(System.in);

System.out.print("Enter a character: ");

String jb = input.nextLine();

char str = jb.charAt(0);

int str2 = (int)str;

System.out.printf(“The Unicode for the character %c is %d”,str,str2);

}

}

4.10

=================================================================

public class disizhang {

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