HDOJ-ACM1071(JAVA) 定积分

import java.io.BufferedInputStream;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scan = new Scanner(new BufferedInputStream(System.in));
        int n = scan.nextInt();
        while(n--!=0){
            double x1 = scan.nextDouble();
            double y1 = scan.nextDouble();
            double x2 = scan.nextDouble();
            double y2 = scan.nextDouble();
            double x3 = scan.nextDouble();
            double y3 = scan.nextDouble();
            double a = ((y2-y1)*(x3-x2)/(x2-x1)-(y3-y2))/((x2*x2-x1*x1)*(x3-x2)/(x2-x1)-(x3*x3-x2*x2));
            double b = ((y2-y1)-a*(x2*x2-x1*x1))/(x2-x1);
            double c = y1-a*x1*x1-b*x1;
            double s = (a/3*x3*x3*x3+b/2*x3*x3+c*x3)-(a/3*x2*x2*x2+b*x2*x2/2+c*x2)-(y3+y2)*(x3-x2)/2;
            System.out.printf("%.2f",s);
            System.out.println();
        }
        scan.close();
    }

}