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AreaOfConvexPolygon.java
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AreaOfConvexPolygon.java
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import java.util.Scanner;
public class AreaOfConvexPolygon{
public static void main(String[] args){
Scanner input = new Scanner(System.in);
System.out.println("Enter the number of points");
int points = input.nextInt();
double[] x = new double[points];
double[] y = new double[points];
double[] side = new double[points - 3];
double[] s = new double[points];
double[] p = new double[points - 2];
int i;
int j;
int k;
int a;
int b;
double sum = 0;
System.out.println("Enter the coordinates of the points");
for (i = 0; i < points ; i++)
{
x[i] = input.nextDouble();
y[i] = input.nextDouble();
}
for(j = 2; j < points - 1; j++)
{
side[j - 2] = Math.sqrt(((x[j] - x[0]) * (x[j] - x[0])) + ((y[j] - y[0]) * (y[j] - y[0])));
}
for(k = 0; k < points; k++)
{
if(k <= points - 2)
{
s[k] = Math.sqrt((x[k + 1] - x[k]) * (x[k + 1] - x[k]) + (y[k + 1] - y[k]) * (y[k + 1] - y[k]));
}
else
s[points - 1] = Math.sqrt((x[points - 1] - x[0]) * (x[points - 1] - x[0]) + (y[points - 1] - y[0]) * (y[points - 1] - y[0]));
}
for(a = 0; a < points - 2; a++)
{
if(a == 0)
{
p[a] = (1.0 / 2) * (s[0] + s[1] + side[0]);
}
else if(a == points - 3)
{
p[a] = (1.0 / 2) * (s[points - 1] + s[points - 2] + side[points - 4]);
}
else
p[a] = (1.0 / 2) * (side[a - 1] + side[a] + s[a + 1]);
}
for(b = 0; b < points - 2; b++)
{
if(b == 0)
{
sum = sum + Math.sqrt(p[0] * (p[0] - s[0]) * (p[0] - s[1]) * (p[0] - side[0]));
}
else if(b == points - 3)
{
sum = sum + Math.sqrt(p[b] * (p[b] - s[points - 1]) * (p[b] - s[points - 2]) * (p[b] - side[b - 1]));
}
else
sum = sum + Math.sqrt(p[b] * (p[b] - side[b - 1]) * (p[b] - side[b]) * (p[b] - s[b + 1]));
}
System.out.println("the total area is" + sum);
}
}